PRIORITY CLAIM
[0001] This application claims the benefit of the filing date of United States Provisional
Patent Application Serial No.
62/133,214, filed March 13, 2015 which is incorporated herein in its entirety.
TECHNICAL FIELD OF THE DISCLOSURE
[0002] The present invention relates generally to genetic control of plant damage caused
by insect pests (
e.g., coleopteran pests). In particular embodiments, the present invention relates to
identification of target coding and non-coding polynucleotides, and the use of recombinant
DNA technologies for post-transcriptionally repressing or inhibiting expression of
target coding and non-coding polynucleotides in the cells of an insect pest to provide
a plant protective effect.
BACKGROUND
[0003] The western corn rootworm (WCR),
Diabrotica virgifera virgifera LeConte, is one of the most devastating corn rootworm species in North America and
is a particular concern in corn-growing areas of the Midwestern United States. The
northern corn rootworm (NCR),
Diabrotica barberi Smith and Lawrence, is a closely-related species that co-inhabits much of the same
range as WCR. There are several other related subspecies of
Diabrotica that are significant pests in the Americas: the Mexican corn rootworm (MCR),
D. virgifera zeae Krysan and Smith; the southern corn rootworm (SCR),
D. undecimpunctata howardi Barber;
D. balteata LeConte;
D.
undecimpunctata tenella; D. speciosa Germar; and
D.
u.
undecimpunctata Mannerheim. The United States Department of Agriculture has estimated that corn rootworms
cause $1 billion in lost revenue each year, including $800 million in yield loss and
$200 million in treatment costs.
[0004] Both WCR and NCR are deposited in the soil as eggs during the summer. The insects
remain in the egg stage throughout the winter. The eggs are oblong, white, and less
than 0.004 inches in length. The larvae hatch in late May or early June, with the
precise timing of egg hatching varying from year to year due to temperature differences
and location. The newly hatched larvae are white worms that are less than 0.125 inches
in length. Once hatched, the larvae begin to feed on corn roots. Corn rootworms go
through three larval instars. After feeding for several weeks, the larvae molt into
the pupal stage. They pupate in the soil, and then emerge from the soil as adults
in July and August. Adult rootworms are about 0.25 inches in length.
[0005] Corn rootworm larvae complete development on corn and several other species of grasses.
Larvae reared on yellow foxtail emerge later and have a smaller head capsule size
as adults than larvae reared on corn.
Ellsbury et al. (2005) Environ. Entomol. 34:627-34. WCR adults feed on corn silk, pollen, and kernels on exposed ear tips. If WCR adults
emerge before corn reproductive tissues are present, they may feed on leaf tissue,
thereby slowing plant growth and occasionally killing the host plant. However, the
adults will quickly shift to preferred silks and pollen when they become available.
NCR adults also feed on reproductive tissues of the corn plant, but in contrast rarely
feed on corn leaves.
[0006] Most of the rootworm damage in corn is caused by larval feeding. Newly hatched rootworms
initially feed on fine corn root hairs and burrow into root tips. As the larvae grow
larger, they feed on and burrow into primary roots. When corn rootworms are abundant,
larval feeding often results in the pruning of roots all the way to the base of the
corn stalk. Severe root injury interferes with the roots' ability to transport water
and nutrients into the plant, reduces plant growth, and results in reduced grain production,
thereby often drastically reducing overall yield. Severe root injury also often results
in lodging of corn plants, which makes harvest more difficult and further decreases
yield. Furthermore, feeding by adults on the corn reproductive tissues can result
in pruning of silks at the ear tip. If this "silk clipping" is severe enough during
pollen shed, pollination may be disrupted.
[0007] Control of corn rootworms may be attempted by crop rotation, chemical insecticides,
biopesticides (
e.g., the spore-forming gram-positive bacterium,
Bacillus thuringiensis (
Bt)), transgenic plants that express
Bt toxins, or a combination thereof. Crop rotation suffers from the disadvantage of
placing unwanted restrictions upon the use of farmland. Moreover, oviposition of some
rootworm species may occur in soybean fields, thereby mitigating the effectiveness
of crop rotation practiced with corn and soybean.
[0008] Chemical insecticides are the most heavily relied upon strategy for achieving corn
rootworm control. Chemical insecticide use, though, is an imperfect corn rootworm
control strategy; over $1 billion may be lost in the United States each year due to
corn rootworm when the costs of the chemical insecticides are added to the costs of
the rootworm damage that may occur despite the use of the insecticides. High populations
of larvae, heavy rains, and improper application of the insecticide(s) may all result
in inadequate corn rootworm control. Furthermore, the continual use of insecticides
may select for insecticide-resistant rootworm strains, as well as raise significant
environmental concerns due to their toxicity to non-target species.
[0009] RNA interference (RNAi) is a process utilizing endogenous cellular pathways, whereby
an interfering RNA (iRNA) molecule
(e.g., a dsRNA molecule) that is specific for all, or any portion of adequate size, of a
target gene results in the degradation of the mRNA encoded thereby. In recent years,
RNAi has been used to perform gene "knockdown" in a number of species and experimental
systems; for example,
Caenorhabditis elegans, plants, insect embryos, and cells in tissue culture.
See,
e.g.,
Fire et al. (1998) Nature 391:806-11;
Martinez et al. (2002) Cell 110:563-74;
McManus and Sharp (2002) Nature Rev. Genetics 3:737-47.
[0010] RNAi accomplishes degradation of mRNA through an endogenous pathway including the
DICER protein complex. DICER cleaves long dsRNA molecules into short fragments of
approximately 20 nucleotides, termed small interfering RNA (siRNA). The siRNA is unwound
into two single-stranded RNAs: the passenger strand and the guide strand. The passenger
strand is degraded, and the guide strand is incorporated into the RNA-induced silencing
complex (RISC). Micro ribonucleic acids (miRNAs) are structurally very similar molecules
that are cleaved from precursor molecules containing a polynucleotide "loop" connecting
the hybridized passenger and guide strands, and they may be similarly incorporated
into RISC. Post-transcriptional gene silencing occurs when the guide strand binds
specifically to a complementary mRNA molecule and induces cleavage by Argonaute, the
catalytic component of the RISC complex. This process is known to spread systemically
throughout the organism despite initially limited concentrations of siRNA and/or miRNA
in some eukaryotes such as plants, nematodes, and some insects.
[0011] Only transcripts complementary to the siRNA and/or miRNA are cleaved and degraded,
and thus the knock-down of mRNA expression is sequence-specific. In plants, several
functional groups of DICER genes exist. The gene silencing effect of RNAi persists
for days and, under experimental conditions, can lead to a decline in abundance of
the targeted transcript of 90% or more, with consequent reduction in levels of the
corresponding protein. In insects, there are at least two DICER genes, where DICER1
facilitates miRNA-directed degradation by Argonaute1.
Lee et al. (2004) Cell 117 (1):69-81. DICER2 facilitates siRNA-directed degradation by Argonaute2.
[0012] U.S. Patent 7,612,194 and
U.S. Patent Publication Nos. 2007/0050860,
2010/0192265, and
2011/0154545 disclose a library of 9112 expressed sequence tag (EST) sequences isolated from
D. v. virgifera LeConte pupae. It is suggested in
U.S. Patent 7,612,194 and
U.S. Patent Publication No. 2007/0050860 to operably link to a promoter a nucleic acid molecule that is complementary to one
of several particular partial sequences of
D. v. virgifera vacuolar-type H
+-ATPase (V-ATPase) disclosed therein for the expression of anti-sense RNA in plant
cells.
U.S. Patent Publication No. 2010/0192265 suggests operably linking a promoter to a nucleic acid molecule that is complementary
to a particular partial sequence of a
D.
v. virgifera gene of unknown and undisclosed function (the partial sequence is stated to be 58%
identical to C56C10.3 gene product in
C.
elegans) for the expression of anti-sense RNA in plant cells.
U.S. Patent Publication No. 2011/0154545 suggests operably linking a promoter to a nucleic acid molecule that is complementary
to two particular partial sequences of
D. v. virgifera coatomer beta subunit genes for the expression of anti-sense RNA in plant cells.
Further,
U.S. Patent 7,943,819 discloses a library of 906 expressed sequence tag (EST) sequences isolated from
D. v. virgifera LeConte larvae, pupae, and dissected midguts, and suggests operably linking a promoter
to a nucleic acid molecule that is complementary to a particular partial sequence
of a
D.
v. virgifera charged multivesicular body protein 4b gene for the expression of double-stranded
RNA in plant cells.
[0013] No further suggestion is provided in
U.S. Patent 7,612,194, and
U.S. Patent Publication Nos. 2007/0050860,
2010/0192265, and
2011/0154545 to use any particular sequence of the more than nine thousand sequences listed therein
for RNA interference, other than the several particular partial sequences of V-ATPase
and the particular partial sequences of genes of unknown function. Furthermore, none
of
U.S. Patent 7,612,194, and
U.S. Patent Publication Nos. 2007/0050860,
2010/0192265, and
2011/0154545 provides any guidance as to which other of the over nine thousand sequences provided
would be lethal, or even otherwise useful, in species of corn rootworm when used as
dsRNA or siRNA.
U.S. Patent 7,943,819 provides no suggestion to use any particular sequence of the more than nine hundred
sequences listed therein for RNA interference, other than the particular partial sequence
of a charged multivesicular body protein 4b gene. Furthermore,
U.S. Patent 7,943,819 provides no guidance as to which other of the over nine hundred sequences provided
would be lethal, or even otherwise useful, in species of corn rootworm when used as
dsRNA or siRNA.
U.S. Patent Application Publication No. U.S. 2013/040173 and
PCT Application Publication No. WO 2013/169923 describe the use of a sequence derived from a
Diabrotica virgifera Snf7 gene for RNA interference in maize. (Also disclosed in
Bolognesi et al. (2012) PLoS ONE 7(10): e47534. doi:10.1371/journal.pone.0047534).
[0014] The overwhelming majority of sequences complementary to corn rootworm DNAs (such
as the foregoing) do not provide a plant protective effect from species of corn rootworm
when used as dsRNA or siRNA. For example,
Baum et al. (2007) Nature Biotechnology 25:1322-1326, describe the effects of inhibiting several WCR gene targets by RNAi. These authors
reported that 8 of the 26 target genes they tested were not able to provide experimentally
significant coleopteran pest mortality at a very high iRNA (
e.g., dsRNA) concentration of more than 520 ng/cm
2.
[0015] The authors of
U.S. Patent 7,612,194 and
U.S. Patent Publication No. 2007/0050860 made the first report of
in planta RNAi in corn plants targeting the western corn rootworm.
Baum et al. (2007) Nat. Biotechnol. 25(11): 1322-6. These authors describe a high-throughput
in vivo dietary RNAi system to screen potential target genes for developing transgenic RNAi
maize. Of an initial gene pool of 290 targets, only 14 exhibited larval control potential.
One of the most effective double-stranded RNAs (dsRNA) targeted a gene encoding vacuolar
ATPase subunit A (V-ATPase), resulting in a rapid suppression of corresponding endogenous
mRNA and triggering a specific RNAi response with low concentrations of dsRNA. Thus,
these authors documented for the first time the potential for
in planta RNAi as a possible pest management tool, while simultaneously demonstrating that
effective targets could not be accurately identified
a priori, even from a relatively small set of candidate genes.
SUMMARY OF THE DISCLOSURE
[0016] Disclosed herein are nucleic acid molecules (
e.g., target genes, DNAs, dsRNAs, siRNAs, miRNAs, and hpRNAs), and methods of use thereof,
for the control of insect pests, including, for example, coleopteran pests, such as
D. v. virgifera LeConte (western corn rootworm, "WCR");
D. barberi Smith and Lawrence (northern corn rootworm, "NCR");
D.
u.
howardi Barber (southern corn rootworm, "SCR");
D. v. zeae Krysan and Smith (Mexican corn rootworm, "MCR");
D. balteata LeConte;
D.
u.
tenella; D. u.
undecimpunctata Mannerheim; and
D. speciosa Germar. In particular examples, exemplary nucleic acid molecules are disclosed that
may be homologous to at least a portion of one or more native nucleic acids in an
insect pest.
[0017] In these and further examples, the native nucleic acid sequence may be a target gene,
the product of which may be, for example and without limitation: involved in a metabolic
process or involved in larval development. In some examples, post-transcriptional
inhibition of the expression of a target gene by a nucleic acid molecule comprising
a polynucleotide homologous thereto may be lethal to an insect pest or result in reduced
growth and/or viability of an insect pest. In specific examples,
RNA polymerase I subunit (referred to herein as, for example,
rpI1,
rpI1-1, or
rpI1-
2) may be selected as a target gene for post-transcriptional silencing. In particular
examples, a target gene useful for post-transcriptional inhibition is an
rpI1 gene is the gene referred to herein as
Diabrotica rpI1-1 (e.g., SEQ ID NO:1) or the gene referred to herein as
Diabrotica rpI1-
2 (e.g., SEQ ID NO:3). An isolated nucleic acid molecule comprising the polynucleotide of
SEQ ID NO: 1; the complement of SEQ ID NO:1; SEQ ID NO:3; the complement of SEQ ID
NO:3; and/or fragments of any of the foregoing
(e.g., SEQ ID NOs:5-8) is therefore disclosed herein.
[0018] Also disclosed are nucleic acid molecules comprising a polynucleotide that encodes
a polypeptide that is at least about 85% identical to an amino acid sequence within
a target gene product (for example, the product of a
rpI1-1 gene). For example, a nucleic acid molecule may comprise a polynucleotide encoding
a polypeptide that is at least 85% identical to SEQ ID NO:2 (
Diabrotica RPI1-1), or SEQ ID NO:4 (
Diabrotica RPI1-2), and/or an amino acid sequence within a product of
Diabrotica rpI1-1 or
Diabrotica rpI1-2. Further disclosed are nucleic acid molecules comprising a polynucleotide that is
the reverse complement of a polynucleotide that encodes a polypeptide at least 85%
identical to an amino acid sequence within a target gene product.
[0019] Also disclosed are cDNA polynucleotides that may be used for the production of iRNA
(
e.g., dsRNA, siRNA, shRNA, miRNA, and hpRNA) molecules that are complementary to all
or part of an insect pest target gene, for example, a
rpI1-1 or
rpI1-2 gene. In particular embodiments, dsRNAs, siRNAs, shRNAs, miRNAs, and/or hpRNAs may
be produced
in vitro or
in vivo by a genetically-modified organism, such as a plant or bacterium. In particular examples,
cDNA molecules are disclosed that may be used to produce iRNA molecules that are complementary
to all or part of an
rpI1-1 or
rpI1-2 gene
(e.g., SEQ ID NO: 1 and SEQ ID NO:3).
[0020] Further disclosed are means for inhibiting expression of an essential gene in a coleopteran
pest, and means for providing coleopteran pest protection to a plant. A means for
inhibiting expression of an essential gene in a coleopteran pest is a single- or double-stranded
RNA molecule consisting of a polynucleotide selected from the group consisting of
SEQ ID NOs:77-80; and the complements thereof. Functional equivalents of means for
inhibiting expression of an essential gene in a coleopteran pest include single- or
double-stranded RNA molecules that are substantially homologous to all or part of
a coleopteran
rpI1 gene comprising SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, and/or SEQ ID NO:8. A means
for providing coleopteran pest protection to a plant is a DNA molecule comprising
a polynucleotide encoding a means for inhibiting expression of an essential gene in
a coleopteran pest operably linked to a promoter, wherein the DNA molecule is capable
of being integrated into the genome of a plant.
[0021] Disclosed are methods for controlling a population of an insect pest
(e.g., a coleopteran pest), comprising providing to an insect pest
(e.g., a coleopteran pest) an iRNA
(e.g., dsRNA, siRNA, shRNA, miRNA, and hpRNA) molecule that functions upon being taken up
by the pest to inhibit a biological function within the pest, wherein the iRNA molecule
comprises all or part of a polynucleotide selected from the group consisting of: SEQ
ID NO:75; the complement of SEQ ID NO:75; SEQ ID NO:76; the complement of SEQ ID NO:76;
SEQ ID NO:77; the complement of SEQ ID NO:77; SEQ ID NO:78; the complement of SEQ
ID NO:78; SEQ ID NO:79; the complement of SEQ ID NO:79; SEQ ID NO:80; the complement
of SEQ ID NO:80; a polynucleotide that hybridizes to a native
rpI1 polynucleotide of an insect
(e.g., WCR); the complement of a polynucleotide that hybridizes to a native
rpI1 polynucleotide of an insect; a polynucleotide that hybridizes to a native coding
polynucleotide of a
Diabrotica organism
(e.g., WCR) comprising all or part of any of SEQ ID NOs:1, 3, and 5-8; the complement of
a polynucleotide that hybridizes to a native coding polynucleotide of a
Diabrotica organism comprising all or part of any of SEQ ID NOs:1, 3, and 5-8.
[0022] In particular embodiments, an iRNA that functions upon being taken up by an insect
pest to inhibit a biological function within the pest is transcribed from a DNA comprising
all or part of a polynucleotide selected from the group consisting of: SEQ ID NO:
1; the complement of SEQ ID NO: 1; SEQ ID NO:3; the complement of SEQ ID NO:3; SEQ
ID NO:5; the complement of SEQ ID NO:5; SEQ ID NO:6; the complement of SEQ ID NO:6;
SEQ ID NO:7; the complement of SEQ ID NO:7; SEQ ID NO:8; the complement of SEQ ID
NO:8; a native coding polynucleotide of a
Diabrotica organism
(e.g., WCR) comprising all or part of any of SEQ ID NOs:1, 3, and 5-8; the complement of
a native coding polynucleotide of a
Diabrotica organism comprising all or part of any of SEQ ID NOs:1, 3, and 5-8.
[0023] Also disclosed herein are methods wherein dsRNAs, siRNAs, shRNAs, miRNAs, and/or
hpRNAs may be provided to an insect pest in a diet-based assay, or in genetically-modified
plant cells expressing the dsRNAs, siRNAs, shRNAs, miRNAs, and/or hpRNAs. In these
and further examples, the dsRNAs, siRNAs, shRNAs, miRNAs, and/or hpRNAs may be ingested
by the pest. Ingestion of dsRNAs, siRNAs, shRNAs, miRNAs, and/or hpRNAs of the invention
may then result in RNAi in the pest, which in turn may result in silencing of a gene
essential for viability of the pest and leading ultimately to mortality. Thus, methods
are disclosed wherein nucleic acid molecules comprising exemplary polynucleotide(s)
useful for control of insect pests are provided to an insect pest. In particular examples,
a coleopteran pest controlled by use of nucleic acid molecules of the invention may
be WCR, NCR, SCR,
D. undecimpunctata howardi,
D. balteata,
D. undecimpunctata tenella,
D. speciosa, or
D.
u.
undecimpunctata.
[0024] The foregoing and other features will become more apparent from the following Detailed
Description of several embodiments, which proceeds with reference to the accompanying
FIGs. 1-2.
BRIEF DESCRIPTION OF THE FIGURES
[0025]
FIG. 1 includes a depiction of a strategy used to provide dsRNA from a single transcription
template with a single pair of primers.
FIG. 2 includes a depiction of a strategy used to provide dsRNA from two transcription templates.
SEQUENCE LISTING
[0026] The nucleic acid sequences listed in the accompanying sequence listing are shown
using standard letter abbreviations for nucleotide bases, as defined in 37 C.F.R.
§ 1.822. The nucleic acid and amino acid sequences listed define molecules (
i.e., polynucleotides and polypeptides, respectively) having the nucleotide and amino
acid monomers arranged in the manner described. The nucleic acid and amino acid sequences
listed also each define a genus of polynucleotides or polypeptides that comprise the
nucleotide and amino acid monomers arranged in the manner described. In view of the
redundancy of the genetic code, it will be understood that a nucleotide sequence including
a coding sequence also describes the genus of polynucleotides encoding the same polypeptide
as a polynucleotide consisting of the reference sequence. It will further be understood
that an amino acid sequence describes the genus of polynucleotide ORFs encoding that
polypeptide.
[0027] Only one strand of each nucleic acid sequence is shown, but the complementary strand
is understood as included by any reference to the displayed strand. As the complement
and reverse complement of a primary nucleic acid sequence are necessarily disclosed
by the primary sequence, the complementary sequence and reverse complementary sequence
of a nucleic acid sequence are included by any reference to the nucleic acid sequence,
unless it is explicitly stated to be otherwise (or it is clear to be otherwise from
the context in which the sequence appears). Furthermore, as it is understood in the
art that the nucleotide sequence of a RNA strand is determined by the sequence of
the DNA from which it was transcribed (but for the substitution of uracil (U) nucleobases
for thymine (T)), a RNA sequence is included by any reference to the DNA sequence
encoding it. In the accompanying sequence listing:
SEQ ID NO:1 shows a contig containing an exemplary Diabrotica rpI1 DNA, also referred to herein in some places as rpI1-1:


SEQ ID NO:2 shows the amino acid sequence of a Diabrotica RPI1 polypeptide, also referred to herein in some places as RPI1-1 encoded by an
exemplary Diabrotica rpI1-1 DNA:


SEQ ID NO:3 shows a contig comprising a further exemplary Diabrotica rpI1 DNA, also referred to herein in some places as rpI1-2:



SEQ ID NO:4 shows the amino acid sequence of a Diabrotica RPI1 polypeptide, also referred to herein in some places as RPI1-2 encoded by an
exemplary Diabrotica rpI1-2 DNA:


SEQ ID NO:5 shows an exemplary Diabrotica rpI1 DNA, referred to herein in some places as rpI1-1 reg1 (region 1), which is used in some examples for the production of a dsRNA:

SEQ ID NO:6 shows a further exemplary Diabrotica rpI1 DNA, referred to herein in some places as rpI1-2 reg2 (region 2), which is used in some examples for the production of a dsRNA:

SEQ ID NO:7 shows a further exemplary Diabrotica rpI1 DNA, referred to herein in some places as rpI1-2 v1 (version 1), which is used in some examples for the production of a dsRNA:

SEQ ID NO:8 shows a further exemplary Diabrotica rpI1 DNA, referred to herein in some places as rpI1-2 v2 (version 2), which is used in some examples for the production of a dsRNA:

SEQ ID NO:9 shows a the nucleotide sequence of T7 phage promoter.
SEQ ID NO: 10 shows an exemplary YFP gene.
SEQ ID NOs:11-18 show primers used to amplify portions of exemplary rpI1 sequences comprising rpI1-1 reg1, rpI1-2 reg2, rpI1-2 v1, and/or rpI1-2 v2, used in some examples for dsRNA production.
SEQ ID NO: 19 shows a DNA sequence of annexin region 1.
SEQ ID NO:20 shows a DNA sequence of annexin region 2.
SEQ ID NO:21 shows a DNA sequence of beta spectrin 2 region 1.
SEQ ID NO:22 shows a DNA sequence of beta spectrin 2 region 2.
SEQ ID NO:23 shows a DNA sequence of mtRP-L4 region 1.
SEQ ID NO:24 shows a DNA sequence of mtRP-L4 region 2.
SEQ ID NOs:25-52 show primers used to amplify gene regions of annexin, beta spectrin 2, mtRP-L4, and YFP for dsRNA synthesis.
SEQ ID NO:53 shows a maize DNA sequence encoding a TIP41-like protein.
SEQ ID NO:54 shows the nucleotide sequence of a T20VN primer oligonucleotide.
SEQ ID NOs:55-59 show primers and probes used for dsRNA transcript expression analyses.
SEQ ID NO:60 shows a nucleotide sequence of a portion of a SpecR coding region used for binary vector backbone detection.
SEQ ID NO:61 shows a nucleotide sequence of an AAD1 coding region used for genomic copy number analysis.
SEQ ID NO:62 shows a DNA sequence of a maize invertase gene.
SEQ ID NOs:63-71 show the nucleotide sequences of DNA oligonucleotides used for gene
copy number determinations and binary vector backbone detection.
SEQ ID NOs:72-74 show primers and probes used for dsRNA transcript maize expression
analyses.
SEQ ID NOs:75-80 show exemplary RNAs transcribed from nucleic acids comprising exemplary
rpI1 polynucleotides and fragments thereof.
SEQ ID NO:81 shows an exemplary DNA encoding a Diabrotica rpI-2 v1 dsRNA; containing a sense polynucleotide, a loop sequence (italics), and an antisense
polynucleotide (underlined font):

SEQ ID NO:82 shows a probe used for dsRNA expression analysis.
SEQ ID NO:83 shows an exemplary DNA nucleotide sequence encoding an intervening loop
in a dsRNA.
SEQ ID NO:84 shows an exemplary dsRNA transcribed from a nucleic acid comprising exemplary
rpI-2 polynucleotide fragments.
DETAILED DESCRIPTION
I. Overview of several embodiments
[0028] We developed RNA interference (RNAi) as a tool for insect pest management, using
one of the most likely target pest species for transgenic plants that express dsRNA;
the western corn rootworm. Thus far, most genes proposed as targets for RNAi in rootworm
larvae do not actually achieve their purpose. Herein, we describe RNAi-mediated knockdown
of
RNA polymerase I largest subunit (
rpI1) in the exemplary insect pest, western corn rootworm, which is shown to have a lethal
phenotype when, for example, iRNA molecules are delivered
via ingested
rpI1 dsRNA. In embodiments herein, the ability to deliver
rpI1 dsRNA by feeding to insects confers an RNAi effect that is very useful for insect
(
e.g., coleopteran) pest management. By combining
rpI1-mediated RNAi with other useful RNAi targets (
e.g., ROP (
U.S. Patent Application Publication No. 14/577811); RNAPII (
U.S. Patent Application Publication No. 14/577854);
RNA polymerase II215 RNAi targets, as described in
U.S. Patent Application No. 62/133202;
RNA polymerase II33 RNAi targets, as described in U.S. Patent Application No.62/133210;
ncm RNAi targets, as described in
U.S. Patent Application No. 62/095487;
Dre4 RNAi targets, as described in
U.S. Patent Application No. 14/705,807;
COPI alpha RNAi targets, as described in
U.S. Patent Application No. 62/063,199;
COPI beta RNAi targets, as described in
U.S. Patent Application No. 62/063,203;
COPI gamma RNAi targets, as described in
U.S. Patent Application No. 62/063,192; and
COPI delta RNAi targets, as described in
U.S. Patent Application No. 62/063,216), the potential to affect multiple target sequences, for example, in rootworms (
e.g., larval rootworms), may increase opportunities to develop sustainable approaches
to insect pest management involving RNAi technologies.
[0029] Disclosed herein are methods and compositions for genetic control of insect
(e.g., coleopteran) pest infestations. Methods for identifying one or more gene(s) essential
to the lifecycle of an insect pest for use as a target gene for RNAi-mediated control
of an insect pest population are also provided. DNA plasmid vectors encoding a RNA
molecule may be designed to suppress one or more target gene(s) essential for growth,
survival, and/or development. In some embodiments, the RNA molecule may be capable
of forming dsRNA molecules. In some embodiments, methods are provided for post-transcriptional
repression of expression or inhibition of a target gene
via nucleic acid molecules that are complementary to a coding or non-coding sequence
of the target gene in an insect pest. In these and further embodiments, a pest may
ingest one or more dsRNA, siRNA, shRNA, miRNA, and/or hpRNA molecules transcribed
from all or a portion of a nucleic acid molecule that is complementary to a coding
or non-coding sequence of a target gene, thereby providing a plant-protective effect.
[0030] Thus, some embodiments involve sequence-specific inhibition of expression of target
gene products, using dsRNA, siRNA, shRNA, miRNA, and/or hpRNA that is complementary
to coding and/or non-coding sequences of the target gene(s) to achieve at least partial
control of an insect (
e.g., coleopteran) pest. Disclosed is a set of isolated and purified nucleic acid molecules
comprising a polynucleotide, for example, as set forth in one of SEQ ID NOs:1, 3,
and fragments thereof. In some embodiments, a stabilized dsRNA molecule may be expressed
from these polynucleotides, fragments thereof, or a gene comprising one of these polynucleotides,
for the post-transcriptional silencing or inhibition of a target gene. In certain
embodiments, isolated and purified nucleic acid molecules comprise all or part of
any of SEQ ID NOs:1; 3; and 5-8.
[0031] Some embodiments involve a recombinant host cell (
e.g., a plant cell) having in its genome at least one recombinant DNA encoding at least
one iRNA (
e.g., dsRNA) molecule(s). In particular embodiments, an encoded dsRNA molecule(s) may
be provided when ingested by an insect (
e.g., coleopteran) pest to post-transcriptionally silence or inhibit the expression of
a target gene in the pest. The recombinant DNA may comprise, for example, any of SEQ
ID NOs:1; 3; and 5-8; fragments of any of SEQ ID NOs:1; 3; and 5-8; a polynucleotide
consisting of a partial sequence of a gene comprising one of SEQ ID NOs:1; 3; and
5-8; and/or complements thereof.
[0032] Some embodiments involve a recombinant host cell having in its genome a recombinant
DNA encoding at least one iRNA (
e.g., dsRNA) molecule(s) comprising all or part of SEQ ID NO:75 or SEQ ID NO:76 (
e.g., at least one polynucleotide selected from a group comprising SEQ ID NOs:77-80). When
ingested by an insect (
e.g., coleopteran) pest, the iRNA molecule(s) may silence or inhibit the expression of
a target
rpI1 DNA
(e.g., a DNA comprising all or part of a polynucleotide selected from the group consisting
of SEQ ID NOs:1, 3, and 5-8) in the pest, and thereby result in cessation of growth,
development, and/or feeding in the pest.
[0033] In some embodiments, a recombinant host cell having in its genome at least one recombinant
DNA encoding at least one RNA molecule capable of forming a dsRNA molecule may be
a transformed plant cell. Some embodiments involve transgenic plants comprising such
a transformed plant cell. In addition to such transgenic plants, progeny plants of
any transgenic plant generation, transgenic seeds, and transgenic plant products,
are all provided, each of which comprises recombinant DNA(s). In particular embodiments,
a RNA molecule capable of forming a dsRNA molecule may be expressed in a transgenic
plant cell. Therefore, in these and other embodiments, a dsRNA molecule may be isolated
from a transgenic plant cell. In particular embodiments, the transgenic plant is a
plant selected from the group comprising corn (
Zea mays) and plants of the family
Poaceae.
[0034] Some embodiments involve a method for modulating the expression of a target gene
in an insect (
e.g., coleopteran) pest cell. In these and other embodiments, a nucleic acid molecule
may be provided, wherein the nucleic acid molecule comprises a polynucleotide encoding
a RNA molecule capable of forming a dsRNA molecule. In particular embodiments, a polynucleotide
encoding a RNA molecule capable of forming a dsRNA molecule may be operatively linked
to a promoter, and may also be operatively linked to a transcription termination sequence.
In particular embodiments, a method for modulating the expression of a target gene
in an insect pest cell may comprise: (a) transforming a plant cell with a vector comprising
a polynucleotide encoding a RNA molecule capable of forming a dsRNA molecule; (b)
culturing the transformed plant cell under conditions sufficient to allow for development
of a plant cell culture comprising a plurality of transformed plant cells; (c) selecting
for a transformed plant cell that has integrated the vector into its genome; and (d)
determining that the selected transformed plant cell comprises the RNA molecule capable
of forming a dsRNA molecule encoded by the polynucleotide of the vector. A plant may
be regenerated from a plant cell that has the vector integrated in its genome and
comprises the dsRNA molecule encoded by the polynucleotide of the vector.
[0035] Thus, also disclosed is a transgenic plant comprising a vector having a polynucleotide
encoding a RNA molecule capable of forming a dsRNA molecule integrated in its genome,
wherein the transgenic plant comprises the dsRNA molecule encoded by the polynucleotide
of the vector. In particular embodiments, expression of a RNA molecule capable of
forming a dsRNA molecule in the plant is sufficient to modulate the expression of
a target gene in a cell of an insect (
e.g., coleopteran) pest that contacts the transformed plant or plant cell (for example,
by feeding on the transformed plant, a part of the plant (
e.g., root) or plant cell), such that growth and/or survival of the pest is inhibited.
Transgenic plants disclosed herein may display protection and/or enhanced protection
to insect pest infestations. Particular transgenic plants may display protection and/or
enhanced protection to one or more coleopteran pest(s) selected from the group consisting
of: WCR; NCR; SCR; MCR;
D. balteata LeConte;
D.
u.
tenella;
D. speciosa Germar; and
D.
u.
undecimpunctata Mannerheim.
[0036] Also disclosed herein are methods for delivery of control agents, such as an iRNA
molecule, to an insect (
e.g., coleopteran) pest. Such control agents may cause, directly or indirectly, an impairment
in the ability of an insect pest population to feed, grow, or otherwise cause damage
in a host. In some embodiments, a method is provided comprising delivery of a stabilized
dsRNA molecule to an insect pest to suppress at least one target gene in the pest,
thereby causing RNAi and reducing or eliminating plant damage in a host of the pest.
In some embodiments, a method of inhibiting expression of a target gene in the insect
pest may result in cessation of growth, survival, and/or development in the pest.
[0037] In some embodiments, compositions (
e.g., a topical composition) are provided that comprise an iRNA (
e.g., dsRNA) molecule for use in plants, animals, and/or the environment of a plant or
animal to achieve the elimination or reduction of an insect (
e.g., coleopteran) pest infestation. In particular embodiments, the composition may be
a nutritional composition or food source to be fed to the insect pest, or an RNAi
bait. Some embodiments comprise making the nutritional composition or food source
available to the pest. Ingestion of a composition comprising iRNA molecules may result
in the uptake of the molecules by one or more cells of the pest, which may in turn
result in the inhibition of expression of at least one target gene in cell(s) of the
pest. Ingestion of or damage to a plant or plant cell by an insect pest infestation
may be limited or eliminated in or on any host tissue or environment in which the
pest is present by providing one or more compositions comprising an iRNA molecule
in the host of the pest.
[0038] The compositions and methods disclosed herein may be used together in combinations
with other methods and compositions for controlling damage by insect
(e.g., coleopteran) pests. For example, an iRNA molecule as described herein for protecting
plants from insect pests may be used in a method comprising the additional use of
one or more chemical agents effective against an insect pest, biopesticides effective
against such a pest, crop rotation, recombinant genetic techniques that exhibit features
different from the features of RNAi-mediated methods and RNAi compositions (
e.g., recombinant production of proteins in plants that are harmful to an insect pest
(
e.g., Bt toxins)), and/or recombinant expression of other iRNA molecules.
II. Abbreviations
[0039]
- dsRNA
- double-stranded ribonucleic acid
- GI
- growth inhibition
- NCBI
- National Center for Biotechnology Information
- gDNA
- genomic Deoxyribonucleic Acid
- iRNA
- inhibitory ribonucleic acid
- ORF
- open reading frame
- RNAi
- ribonucleic acid interference
- miRNA
- micro ribonucleic acid
- shRNA
- small hairpin ribonucleic acid
- siRNA
- small inhibitory ribonucleic acid
- hpRNA
- hairpin ribonucleic acid
- UTR
- untranslated region
- WCR
- Western corn rootworm (Diabrotica virgifera virgifera LeConte)
- NCR
- Northern corn rootworm (Diabrotica barberi Smith and Lawrence)
- MCR
- Mexican corn rootworm (Diabrotica virgifera zeae Krysan and Smith)
- PCR
- Polymerase chain reaction
- qPCR
- quantitative polymerase chain reaction
- RISC
- RNA-induced Silencing Complex
- SCR
- Southern corn rootworm (Diabrotica undecimpunctata howardi Barber)
- SEM
- standard error of the mean
- YFP
- yellow fluorescent protein
III. Terms
[0040] In the description and tables which follow, a number of terms are used. In order
to provide a clear and consistent understanding of the specification and claims, including
the scope to be given such terms, the following definitions are provided:
Coleopteran pest: As used herein, the term "coleopteran pest" refers to pest insects
of the order Coleoptera, including pest insects in the genus Diabrotica, which feed upon agricultural crops and crop products, including corn and other true
grasses. In particular examples, a coleopteran pest is selected from a list comprising
D. v. virgifera LeConte (WCR); D. barberi Smith and Lawrence (NCR); D. u. howardi (SCR); D. v. zeae (MCR); D. balteata LeConte; D. u. tenella; D. speciosa Germar; and D. u. undecimpunctata Mannerheim.
Contact (with an organism): As used herein, the term "contact with" or "uptake by"
an organism (e.g., a coleopteran pest), with regard to a nucleic acid molecule, includes internalization
of the nucleic acid molecule into the organism, for example and without limitation:
ingestion of the molecule by the organism (e.g., by feeding); contacting the organism with a composition comprising the nucleic
acid molecule; and soaking of organisms with a solution comprising the nucleic acid
molecule.
Contig: As used herein the term "contig" refers to a DNA sequence that is reconstructed
from a set of overlapping DNA segments derived from a single genetic source.
Corn plant: As used herein, the term "corn plant" refers to a plant of the species,
Zea mays (maize).
Expression: As used herein, "expression" of a coding polynucleotide (for example,
a gene or a transgene) refers to the process by which the coded information of a nucleic
acid transcriptional unit (including, e.g., gDNA or cDNA) is converted into an operational, non-operational, or structural part
of a cell, often including the synthesis of a protein. Gene expression can be influenced
by external signals; for example, exposure of a cell, tissue, or organism to an agent
that increases or decreases gene expression. Expression of a gene can also be regulated
anywhere in the pathway from DNA to RNA to protein. Regulation of gene expression
occurs, for example, through controls acting on transcription, translation, RNA transport
and processing, degradation of intermediary molecules such as mRNA, or through activation,
inactivation, compartmentalization, or degradation of specific protein molecules after
they have been made, or by combinations thereof. Gene expression can be measured at
the RNA level or the protein level by any method known in the art, including, without
limitation, northern blot, RT-PCR, western blot, or in vitro, in situ, or in vivo protein activity assay(s).
Genetic material: As used herein, the term "genetic material" includes all genes,
and nucleic acid molecules, such as DNA and RNA.
Inhibition: As used herein, the term "inhibition," when used to describe an effect
on a coding polynucleotide (for example, a gene), refers to a measurable decrease
in the cellular level of mRNA transcribed from the coding polynucleotide and/or peptide,
polypeptide, or protein product of the coding polynucleotide. In some examples, expression
of a coding polynucleotide may be inhibited such that expression is approximately
eliminated. "Specific inhibition" refers to the inhibition of a target coding polynucleotide
without consequently affecting expression of other coding polynucleotides (e.g., genes) in the cell wherein the specific inhibition is being accomplished.
Insect: As used herein with regard to pests, the term "insect pest" specifically includes
coleopteran insect pests. In some examples, the term "insect pest" specifically refers
to a coleopteran pest in the genus Diabrotica selected from a list comprising D. v. virgifera LeConte (WCR); D. barberi Smith and Lawrence (NCR); D. u. howardi (SCR); D. v. zeae (MCR); D. balteata LeConte; D. u. tenella; D. speciosa Germar, and D. u. undecimpunctata Mannerheim.
Isolated: An "isolated" biological component (such as a nucleic acid or protein) has
been substantially separated, produced apart from, or purified away from other biological
components in the cell of the organism in which the component naturally occurs (i.e., other chromosomal and extra-chromosomal DNA and RNA, and proteins), while effecting
a chemical or functional change in the component (e.g., a nucleic acid may be isolated from a chromosome by breaking chemical bonds connecting
the nucleic acid to the remaining DNA in the chromosome). Nucleic acid molecules and
proteins that have been "isolated" include nucleic acid molecules and proteins purified
by standard purification methods. The term also embraces nucleic acids and proteins
prepared by recombinant expression in a host cell, as well as chemically-synthesized
nucleic acid molecules, proteins, and peptides.
Nucleic acid molecule: As used herein, the term "nucleic acid molecule" may refer
to a polymeric form of nucleotides, which may include both sense and anti-sense strands
of RNA, cDNA, gDNA, and synthetic forms and mixed polymers of the above. A nucleotide
or nucleobase may refer to a ribonucleotide, deoxyribonucleotide, or a modified form
of either type of nucleotide. A "nucleic acid molecule" as used herein is synonymous
with "nucleic acid" and "polynucleotide." A nucleic acid molecule is usually at least
10 bases in length, unless otherwise specified. By convention, the nucleotide sequence
of a nucleic acid molecule is read from the 5' to the 3' end of the molecule. The
"complement" of a nucleic acid molecule refers to a polynucleotide having nucleobases
that may form base pairs with the nucleobases of the nucleic acid molecule (i.e., A-T/U, and G-C).
[0041] Some embodiments include nucleic acids comprising a template DNA that is transcribed
into a RNA molecule that is the complement of a mRNA molecule. In these embodiments,
the complement of the nucleic acid transcribed into the mRNA molecule is present in
the 5' to 3' orientation, such that RNA polymerase (which transcribes DNA in the 5'
to 3' direction) will transcribe a nucleic acid from the complement that can hybridize
to the mRNA molecule. Unless explicitly stated otherwise, or it is clear to be otherwise
from the context, the term "complement" therefore refers to a polynucleotide having
nucleobases, from 5' to 3', that may form base pairs with the nucleobases of a reference
nucleic acid. Similarly, unless it is explicitly stated to be otherwise (or it is
clear to be otherwise from the context), the "reverse complement" of a nucleic acid
refers to the complement in reverse orientation. The foregoing is demonstrated in
the following illustration:
- ATGATGATG
- polynucleotide
- TACTACTAC
- "complement" of the polynucleotide
- CATCATCAT
- "reverse complement" of the polynucleotide
[0042] Some embodiments of the invention may include hairpin RNA-forming RNAi molecules.
In these RNAi molecules, both the complement of a nucleic acid to be targeted by RNA
interference and the reverse complement may be found in the same molecule, such that
the single-stranded RNA molecule may "fold over" and hybridize to itself over a region
comprising the complementary and reverse complementary polynucleotides.
[0043] "Nucleic acid molecules" include all polynucleotides, for example: single- and double-stranded
forms of DNA; single-stranded forms of RNA; and double-stranded forms of RNA (dsRNA).
The term "nucleotide sequence" or "nucleic acid sequence" refers to both the sense
and antisense strands of a nucleic acid as either individual single strands or in
the duplex. The term "ribonucleic acid" (RNA) is inclusive of iRNA (inhibitory RNA),
dsRNA (double stranded RNA), siRNA (small interfering RNA), shRNA (small hairpin RNA),
mRNA (messenger RNA), miRNA (micro-RNA), hpRNA (hairpin RNA), tRNA (transfer RNAs,
whether charged or discharged with a corresponding acylated amino acid), and cRNA
(complementary RNA). The term "deoxyribonucleic acid" (DNA) is inclusive of cDNA,
gDNA, and DNA-RNA hybrids. The terms " polynucleotide" and "nucleic acid," and "fragments"
thereof will be understood by those in the art as a term that includes both gDNAs,
ribosomal RNAs, transfer RNAs, messenger RNAs, operons, and smaller engineered polynucleotides
that encode or may be adapted to encode, peptides, polypeptides, or proteins.
[0044] Oligonucleotide: An oligonucleotide is a short nucleic acid polymer. Oligonucleotides
may be formed by cleavage of longer nucleic acid segments, or by polymerizing individual
nucleotide precursors. Automated synthesizers allow the synthesis of oligonucleotides
up to several hundred bases in length. Because oligonucleotides may bind to a complementary
nucleic acid, they may be used as probes for detecting DNA or RNA. Oligonucleotides
composed of DNA (oligodeoxyribonucleotides) may be used in PCR, a technique for the
amplification of DNAs. In PCR, the oligonucleotide is typically referred to as a "primer,"
which allows a DNA polymerase to extend the oligonucleotide and replicate the complementary
strand.
[0045] A nucleic acid molecule may include either or both naturally occurring and modified
nucleotides linked together by naturally occurring and/or non-naturally occurring
nucleotide linkages. Nucleic acid molecules may be modified chemically or biochemically,
or may contain non-natural or derivatized nucleotide bases, as will be readily appreciated
by those of skill in the art. Such modifications include, for example, labels, methylation,
substitution of one or more of the naturally occurring nucleotides with an analog,
internucleotide modifications (
e.g., uncharged linkages: for example, methyl phosphonates, phosphotriesters, phosphoramidates,
carbamates,
etc.; charged linkages: for example, phosphorothioates, phosphorodithioates,
etc.; pendent moieties: for example, peptides; intercalators: for example, acridine, psoralen,
etc.; chelators; alkylators; and modified linkages: for example, alpha anomeric nucleic
acids,
etc.)
. The term "nucleic acid molecule" also includes any topological conformation, including
single-stranded, double-stranded, partially duplexed, triplexed, hairpinned, circular,
and padlocked conformations.
[0046] As used herein with respect to DNA, the term "coding polynucleotide," "structural
polynucleotide," or "structural nucleic acid molecule" refers to a polynucleotide
that is ultimately translated into a polypeptide,
via transcription and mRNA, when placed under the control of appropriate regulatory elements.
With respect to RNA, the term "coding polynucleotide" refers to a polynucleotide that
is translated into a peptide, polypeptide, or protein. The boundaries of a coding
polynucleotide are determined by a translation start codon at the 5'-terminus and
a translation stop codon at the 3'-terminus. Coding polynucleotides include, but are
not limited to: gDNA; cDNA; EST; and recombinant polynucleotides.
[0047] As used herein, "transcribed non-coding polynucleotide" refers to segments of mRNA
molecules such as 5'UTR, 3'UTR, and intron segments that are not translated into a
peptide, polypeptide, or protein. Further, "transcribed non-coding polynucleotide"
refers to a nucleic acid that is transcribed into a RNA that functions in the cell,
for example, structural RNAs
(e.g., ribosomal RNA (rRNA) as exemplified by 5S rRNA, 5.8S rRNA, 16S rRNA, 18S rRNA, 23S
rRNA, and 28S rRNA, and the like); transfer RNA (tRNA); and snRNAs such as U4, U5,
U6, and the like. Transcribed non-coding polynucleotides also include, for example
and without limitation, small RNAs (sRNA), which term is often used to describe small
bacterial non-coding RNAs; small nucleolar RNAs (snoRNA); microRNAs; small interfering
RNAs (siRNA); Piwi-interacting RNAs (piRNA); and long non-coding RNAs. Further still,
"transcribed non-coding polynucleotide" refers to a polynucleotide that may natively
exist as an intragenic "spacer" in a nucleic acid and which is transcribed into a
RNA molecule.
[0048] Lethal RNA interference: As used herein, the term "lethal RNA interference" refers
to RNA interference that results in death or a reduction in viability of the subject
individual to which, for example, a dsRNA, miRNA, siRNA, shRNA, and/or hpRNA is delivered.
[0049] Genome: As used herein, the term "genome" refers to chromosomal DNA found within
the nucleus of a cell, and also refers to organelle DNA found within subcellular components
of the cell. In some embodiments of the invention, a DNA molecule may be introduced
into a plant cell, such that the DNA molecule is integrated into the genome of the
plant cell. In these and further embodiments, the DNA molecule may be either integrated
into the nuclear DNA of the plant cell, or integrated into the DNA of the chloroplast
or mitochondrion of the plant cell. The term "genome," as it applies to bacteria,
refers to both the chromosome and plasmids within the bacterial cell. In some embodiments
of the invention, a DNA molecule may be introduced into a bacterium such that the
DNA molecule is integrated into the genome of the bacterium. In these and further
embodiments, the DNA molecule may be either chromosomally-integrated or located as
or in a stable plasmid.
[0050] Sequence identity: The term "sequence identity" or "identity," as used herein in
the context of two polynucleotides or polypeptides, refers to the residues in the
sequences of the two molecules that are the same when aligned for maximum correspondence
over a specified comparison window.
[0051] As used herein, the term "percentage of sequence identity" may refer to the value
determined by comparing two optimally aligned sequences (
e.g., nucleic acid sequences or polypeptide sequences) of a molecule over a comparison
window, wherein the portion of the sequence in the comparison window may comprise
additions or deletions (
i.e., gaps) as compared to the reference sequence (which does not comprise additions or
deletions) for optimal alignment of the two sequences. The percentage is calculated
by determining the number of positions at which the identical nucleotide or amino
acid residue occurs in both sequences to yield the number of matched positions, dividing
the number of matched positions by the total number of positions in the comparison
window, and multiplying the result by 100 to yield the percentage of sequence identity.
A sequence that is identical at every position in comparison to a reference sequence
is said to be 100% identical to the reference sequence, and vice-versa.
[0053] The National Center for Biotechnology Information (NCBI)
Basic
Local
Alignment
Search
Tool (BLAST™; Altschul
et al. (1990)) is available from several sources, including the National Center for Biotechnology
Information (Bethesda, MD), and on the internet, for use in connection with several
sequence analysis programs. A description of how to determine sequence identity using
this program is available on the internet under the "help" section for BLAST™. For
comparisons of nucleic acid sequences, the "Blast 2 sequences" function of the BLAST™
(Blastn) program may be employed using the default BLOSUM62 matrix set to default
parameters. Nucleic acids with even greater sequence similarity to the sequences of
the reference polynucleotides will show increasing percentage identity when assessed
by this method.
[0054] Specifically hybridizable/Specifically complementary: As used herein, the terms "Specifically
hybridizable" and "Specifically complementary" are terms that indicate a sufficient
degree of complementarity such that stable and specific binding occurs between the
nucleic acid molecule and a target nucleic acid molecule. Hybridization between two
nucleic acid molecules involves the formation of an anti-parallel alignment between
the nucleobases of the two nucleic acid molecules. The two molecules are then able
to form hydrogen bonds with corresponding bases on the opposite strand to form a duplex
molecule that, if it is sufficiently stable, is detectable using methods well known
in the art. A polynucleotide need not be 100% complementary to its target nucleic
acid to be specifically hybridizable. However, the amount of complementarity that
must exist for hybridization to be specific is a function of the hybridization conditions
used.
[0055] Hybridization conditions resulting in particular degrees of stringency will vary
depending upon the nature of the hybridization method of choice and the composition
and length of the hybridizing nucleic acids. Generally, the temperature of hybridization
and the ionic strength (especially the Na
+ and/or Mg
++ concentration) of the hybridization buffer will determine the stringency of hybridization,
though wash times also influence stringency. Calculations regarding hybridization
conditions required for attaining particular degrees of stringency are known to those
of ordinary skill in the art, and are discussed, for example, in
Sambrook et al. (ed.) Molecular Cloning: A Laboratory Manual, 2nd ed., vol. 1-3, Cold
Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989, chapters 9 and 11; and
Hames and Higgins (eds.) Nucleic Acid Hybridization, IRL Press, Oxford, 1985. Further detailed instruction and guidance with regard to the hybridization of nucleic
acids may be found, for example, in
Tijssen, "Overview of principles of hybridization and the strategy of nucleic acid
probe assays," in Laboratory Techniques in Biochemistry and Molecular Biology- Hybridization
with Nucleic Acid Probes, Part I, Chapter 2, Elsevier, NY, 1993; and
Ausubel et al., Eds., Current Protocols in Molecular Biology, Chapter 2, Greene Publishing
and Wiley-Interscience, NY, 1995.
[0056] As used herein, "stringent conditions" encompass conditions under which hybridization
will only occur if there is less than 20% mismatch between the sequence of the hybridization
molecule and a homologous polynucleotide within the target nucleic acid molecule.
"Stringent conditions" include further particular levels of stringency. Thus, as used
herein, "moderate stringency" conditions are those under which molecules with more
than 20% sequence mismatch will not hybridize; conditions of "high stringency" are
those under which sequences with more than 10% mismatch will not hybridize; and conditions
of "very high stringency" are those under which sequences with more than 5% mismatch
will not hybridize.
[0057] The following are representative, non-limiting hybridization conditions. High Stringency
condition (detects polynucleotides that share at least 90% sequence identity): Hybridization
in 5x SSC buffer at 65 °C for 16 hours; wash twice in 2x SSC buffer at room temperature
for 15 minutes each; and wash twice in 0.5x SSC buffer at 65 °C for 20 minutes each.
[0058] Moderate Stringency condition (detects polynucleotides that share at least 80% sequence
identity): Hybridization in 5x-6x SSC buffer at 65-70 °C for 16-20 hours; wash twice
in 2x SSC buffer at room temperature for 5-20 minutes each; and wash twice in 1x SSC
buffer at 55-70 °C for 30 minutes each.
[0059] Non-stringent control condition (polynucleotides that share at least 50% sequence
identity will hybridize): Hybridization in 6x SSC buffer at room temperature to 55
°C for 16-20 hours; wash at least twice in 2x-3x SSC buffer at room temperature to
55 °C for 20-30 minutes each.
[0060] As used herein, the term "substantially homologous" or "substantial homology," with
regard to a nucleic acid, refers to a polynucleotide having contiguous nucleobases
that hybridize under stringent conditions to the reference nucleic acid. For example,
nucleic acids that are substantially homologous to a reference nucleic acid of any
of SEQ ID NOs:1, 3, and 5-8 are those nucleic acids that hybridize under stringent
conditions (
e.g., the Moderate Stringency conditions set forth,
supra) to the reference nucleic acid. Substantially homologous polynucleotides may have
at least 80% sequence identity. For example, substantially homologous polynucleotides
may have from about 80% to 100% sequence identity, such as 79%; 80%; about 81%; about
82%; about 83%; about 84%; about 85%; about 86%; about 87%; about 88%; about 89%;
about 90%; about 91%; about 92%; about 93%; about 94% about 95%; about 96%; about
97%; about 98%; about 98.5%; about 99%; about 99.5%; and about 100%. The property
of substantial homology is closely related to specific hybridization. For example,
substantially homologous polynucleotides may have from about 80% to 100% sequence
identity to SEQ ID NO: 1, such as 79%; 80%; about 81%; about 82%; about 83%; about
84%; about 85%; about 86%; about 87%; about 88%; about 89%; about 90%; about 91%;
about 92%; about 93%; about 94% about 95%; about 96%; about 97%; about 98%; about
98.5%; about 99%; about 99.5%; and about 100% to SEQ ID NO:1. For example, substantially
homologous polynucleotides may have from about 80% to 100% sequence identity to SEQ
ID NO:3, such as 79%; 80%; about 81%; about 82%; about 83%; about 84%; about 85%;
about 86%; about 87%; about 88%; about 89%; about 90%; about 91%; about 92%; about
93%; about 94% about 95%; about 96%; about 97%; about 98%; about 98.5%; about 99%;
about 99.5%; and about 100% to SEQ ID NO:3. For example, substantially homologous
polynucleotides may have from about 80% to 100% sequence identity to SEQ ID NO:5,
such as 79%; 80%; about 81%; about 82%; about 83%; about 84%; about 85%; about 86%;
about 87%; about 88%; about 89%; about 90%; about 91%; about 92%; about 93%; about
94% about 95%; about 96%; about 97%; about 98%; about 98.5%; about 99%; about 99.5%;
and about 100% to SEQ ID NO:5. For example, substantially homologous polynucleotides
may have from about 80% to 100% sequence identity to SEQ ID NO:6, such as 79%; 80%;
about 81%; about 82%; about 83%; about 84%; about 85%; about 86%; about 87%; about
88%; about 89%; about 90%; about 91%; about 92%; about 93%; about 94% about 95%; about
96%; about 97%; about 98%; about 98.5%; about 99%; about 99.5%; and about 100% to
SEQ ID NO:6. For example, substantially homologous polynucleotides may have from about
80% to 100% sequence identity to SEQ ID NO:7, such as 79%; 80%; about 81%; about 82%;
about 83%; about 84%; about 85%; about 86%; about 87%; about 88%; about 89%; about
90%; about 91%; about 92%; about 93%; about 94% about 95%; about 96%; about 97%; about
98%; about 98.5%; about 99%; about 99.5%; and about 100% to SEQ ID NO:7. For example,
substantially homologous polynucleotides may have from about 80% to 100% sequence
identity to SEQ ID NO:8, such as 79%; 80%; about 81%; about 82%; about 83%; about
84%; about 85%; about 86%; about 87%; about 88%; about 89%; about 90%; about 91%;
about 92%; about 93%; about 94% about 95%; about 96%; about 97%; about 98%; about
98.5%; about 99%; about 99.5%; and about 100% to SEQ ID NO:8. For example, a nucleic
acid molecule is specifically hybridizable when there is a sufficient degree of complementarity
to avoid non-specific binding of the nucleic acid to non-target polynucleotides under
conditions where specific binding is desired, for example, under stringent hybridization
conditions.
[0061] As used herein, the term "ortholog" refers to a gene in two or more species that
has evolved from a common ancestral nucleic acid, and may retain the same function
in the two or more species.
[0062] As used herein, two nucleic acid molecules are said to exhibit "complete complementarity"
when every nucleotide of a polynucleotide read in the 5' to 3' direction is complementary
to every nucleotide of the other polynucleotide when read in the 3' to 5' direction.
A polynucleotide that is complementary to a reference polynucleotide will exhibit
a sequence identical to the reverse complement of the reference polynucleotide. These
terms and descriptions are well defined in the art and are easily understood by those
of ordinary skill in the art.
[0063] Operably linked: A first polynucleotide is operably linked with a second polynucleotide
when the first polynucleotide is in a functional relationship with the second polynucleotide.
When recombinantly produced, operably linked polynucleotides are generally contiguous,
and, where necessary to join two protein-coding regions, in the same reading frame
(e.g., in a translationally fused ORF). However, nucleic acids need not be contiguous to
be operably linked.
[0064] The term, "operably linked," when used in reference to a regulatory genetic element
and a coding polynucleotide, means that the regulatory element affects the expression
of the linked coding polynucleotide. "Regulatory elements," or "control elements,"
refer to polynucleotides that influence the timing and level/amount of transcription,
RNA processing or stability, or translation of the associated coding polynucleotide.
Regulatory elements may include promoters; translation leaders; introns; enhancers;
stem-loop structures; repressor binding polynucleotides; polynucleotides with a termination
sequence; polynucleotides with a polyadenylation recognition sequence;
etc. Particular regulatory elements may be located upstream and/or downstream of a coding
polynucleotide operably linked thereto. Also, particular regulatory elements operably
linked to a coding polynucleotide may be located on the associated complementary strand
of a double-stranded nucleic acid molecule.
[0065] Promoter: As used herein, the term "promoter" refers to a region of DNA that may
be upstream from the start of transcription, and that may be involved in recognition
and binding of RNA polymerase and other proteins to initiate transcription. A promoter
may be operably linked to a coding polynucleotide for expression in a cell, or a promoter
may be operably linked to a polynucleotide encoding a signal peptide which may be
operably linked to a coding polynucleotide for expression in a cell. A "plant promoter"
may be a promoter capable of initiating transcription in plant cells. Examples of
promoters under developmental control include promoters that preferentially initiate
transcription in certain tissues, such as leaves, roots, seeds, fibers, xylem vessels,
tracheids, or sclerenchyma. Such promoters are referred to as "tissue-preferred".
Promoters which initiate transcription only in certain tissues are referred to as
"tissue-specific". A "cell type-specific" promoter primarily drives expression in
certain cell types in one or more organs, for example, vascular cells in roots or
leaves. An "inducible" promoter may be a promoter which may be under environmental
control. Examples of environmental conditions that may initiate transcription by inducible
promoters include anaerobic conditions and the presence of light. Tissue-specific,
tissue-preferred, cell type specific, and inducible promoters constitute the class
of "non-constitutive" promoters. A "constitutive" promoter is a promoter which may
be active under most environmental conditions or in most tissue or cell types.
[0066] Any inducible promoter can be used in some embodiments of the invention.
See Ward et al. (1993) Plant Mol. Biol. 22:361-366. With an inducible promoter, the rate of transcription increases in response to an
inducing agent. Exemplary inducible promoters include, but are not limited to: Promoters
from the ACEI system that respond to copper;
In2 gene from maize that responds to benzenesulfonamide herbicide safeners; Tet repressor
from Tn10; and the inducible promoter from a steroid hormone gene, the transcriptional
activity of which may be induced by a glucocorticosteroid hormone (
Schena et al. (1991) Proc. Natl. Acad. Sci. USA 88:0421).
[0067] Exemplary constitutive promoters include, but are not limited to: Promoters from
plant viruses, such as the 35S promoter from Cauliflower Mosaic Virus (CaMV); promoters
from rice actin genes; ubiquitin promoters; pEMU; MAS; maize H3 histone promoter;
and the ALS promoter,
Xba1/
NcoI fragment 5' to the
Brassica napus ALS3 structural gene (or a polynucleotide similar to said
Xba1/
NcoI fragment) (International
PCT Publication No. WO96/30530).
[0068] Additionally, any tissue-specific or tissue-preferred promoter may be utilized in
some embodiments of the invention. Plants transformed with a nucleic acid molecule
comprising a coding polynucleotide operably linked to a tissue-specific promoter may
produce the product of the coding polynucleotide exclusively, or preferentially, in
a specific tissue. Exemplary tissue-specific or tissue-preferred promoters include,
but are not limited to: A seed-preferred promoter, such as that from the phaseolin
gene; a leaf-specific and light-induced promoter such as that from
cab or
rubisco; an anther-specific promoter such as that from
LAT52; a pollen-specific promoter such as that from
Zm13; and a microspore-preferred promoter such as that from
apg.
[0070] Transgene: An exogenous nucleic acid. In some examples, a transgene may be a DNA
that encodes one or both strand(s) of a RNA capable of forming a dsRNA molecule that
comprises a polynucleotide that is complementary to a nucleic acid molecule found
in a coleopteran pest. In further examples, a transgene may be an antisense polynucleotide,
wherein expression of the antisense polynucleotide inhibits expression of a target
nucleic acid, thereby producing an RNAi phenotype. In still further examples, a transgene
may be a gene
(e.g., a herbicide-tolerance gene, a gene encoding an industrially or pharmaceutically useful
compound, or a gene encoding a desirable agricultural trait). In these and other examples,
a transgene may contain regulatory elements operably linked to a coding polynucleotide
of the transgene
(e.g., a promoter).
[0071] Vector: A nucleic acid molecule as introduced into a cell, for example, to produce
a transformed cell. A vector may include genetic elements that permit it to replicate
in the host cell, such as an origin of replication. Examples of vectors include, but
are not limited to: a plasmid; cosmid; bacteriophage; or virus that carries exogenous
DNA into a cell. A vector may also include one or more genes, including ones that
produce antisense molecules, and/or selectable marker genes and other genetic elements
known in the art. A vector may transduce, transform, or infect a cell, thereby causing
the cell to express the nucleic acid molecules and/or proteins encoded by the vector.
A vector optionally includes materials to aid in achieving entry of the nucleic acid
molecule into the cell
(e.g., a liposome, protein coating,
etc.)
.
[0072] Yield: A stabilized yield of about 100% or greater relative to the yield of check
varieties in the same growing location growing at the same time and under the same
conditions. In particular embodiments, "improved yield" or "improving yield" means
a cultivar having a stabilized yield of 105% or greater relative to the yield of check
varieties in the same growing location containing significant densities of the coleopteran
pests that are injurious to that crop growing at the same time and under the same
conditions, which are targeted by the compositions and methods herein.
[0073] Unless specifically indicated or implied, the terms "a," "an," and "the" signify
"at least one," as used herein.
[0074] Unless otherwise specifically explained, all technical and scientific terms used
herein have the same meaning as commonly understood by those of ordinary skill in
the art to which this disclosure belongs. Definitions of common terms in molecular
biology can be found in, for example,
Lewin's Genes X, Jones & Bartlett Publishers, 2009 (ISBN 10 0763766321);
Krebs et al. (eds.), The Encyclopedia of Molecular Biology, Blackwell Science Ltd.,
1994 (ISBN 0-632-02182-9); and
Meyers R.A. (ed.), Molecular Biology and Biotechnology: A Comprehensive Desk Reference,
VCH Publishers, Inc., 1995 (ISBN 1-56081-569-8). All percentages are by weight and all solvent mixture proportions are by volume
unless otherwise noted. All temperatures are in degrees Celsius.
IV. Nucleic Acid Molecules Comprising an Insect Pest Sequence
A. Overview
[0075] Described herein are nucleic acid molecules useful for the control of insect pests.
In some examples, the insect pest is a coleopteran insect pest (
e.g., a coleopteran pest in the genus
Diabrotica)
. Described nucleic acid molecules include target polynucleotides
(e.g., native genes, and non-coding polynucleotides), dsRNAs, siRNAs, shRNAs, hpRNAs, and
miRNAs. For example, dsRNA, siRNA, miRNA, shRNA, and/or hpRNA molecules are described
in some embodiments that may be specifically complementary to all or part of one or
more native nucleic acids in a coleopteran pest. In these and further embodiments,
the native nucleic acid(s) may be one or more target gene(s), the product of which
may be, for example and without limitation: involved in a metabolic process or involved
in larval development. Nucleic acid molecules described herein, when introduced into
a cell comprising at least one native nucleic acid(s) to which the nucleic acid molecules
are specifically complementary, may initiate RNAi in the cell, and consequently reduce
or eliminate expression of the native nucleic acid(s). In some examples, reduction
or elimination of the expression of a target gene by a nucleic acid molecule specifically
complementary thereto may result in reduction or cessation of growth, development,
and/or feeding in the pest.
[0076] In some embodiments, at least one target gene in an insect pest may be selected,
wherein the target gene comprises a
rpI1 polynucleotide. In particular examples, a target gene in a coleopteran pest is selected,
wherein the target gene comprises a polynucleotide selected from among SEQ ID NOs:1,
3, and 5-8.
[0077] In some embodiments, a target gene may be a nucleic acid molecule comprising a polynucleotide
that can be reverse translated
in silico to a polypeptide comprising a contiguous amino acid sequence that is at least about
85% identical
(e.g., at least 84%, 85%, about 90%, about 95%, about 96%, about 97%, about 98%, about 99%,
about 100%, or 100% identical) to the amino acid sequence of a protein product of
an
rpI1 polynucleotide. A target gene may be any
rpI1 polynucleotide in an insect pest, the post-transcriptional inhibition of which has
a deleterious effect on the growth, survival, and/or viability of the pest, for example,
to provide a protective benefit against the pest to a plant. In particular examples,
a target gene is a nucleic acid molecule comprising a polynucleotide that can be reverse
translated
in silico to a polypeptide comprising a contiguous amino acid sequence that is at least about
85% identical, about 90% identical, about 95% identical, about 96% identical, about
97% identical, about 98% identical, about 99% identical, about 100% identical, or
100% identical to the amino acid sequence of SEQ ID NO:2 or at least about 85% identical,
about 90% identical, about 95% identical, about 96% identical, about 97% identical,
about 98% identical, about 99% identical, about 100% identical, or 100% identical
to the amino acid sequence of SEQ ID NO:4.
[0078] Provided according to the invention are DNAs, the expression of which results in
a RNA molecule comprising a polynucleotide that is specifically complementary to all
or part of a native RNA molecule that is encoded by a coding polynucleotide in an
insect (
e.g., coleopteran) pest. In some embodiments, after ingestion of the expressed RNA molecule
by an insect pest, down-regulation of the coding polynucleotide in cells of the pest
may be obtained. In particular embodiments, down-regulation of the coding polynucleotide
in cells of the pest may be obtained. In particular embodiments, down-regulation of
the coding polynucleotide in cells of the insect pest results in a deleterious effect
on the growth and/or development of the pest.
[0079] In some embodiments, target polynucleotides include transcribed non-coding RNAs,
such as 5'UTRs; 3'UTRs; spliced leaders; introns; outrons (
e.g., 5'UTR RNA subsequently modified in trans splicing); donatrons (
e.g., non-coding RNA required to provide donor sequences for
trans splicing); and other non-coding transcribed RNA of target insect pest genes. Such
polynucleotides may be derived from both mono-cistronic and poly-cistronic genes.
[0080] Thus, also described herein in connection with some embodiments are iRNA molecules
(
e.g., dsRNAs, siRNAs, miRNAs, shRNAs, and hpRNAs) that comprise at least one polynucleotide
that is specifically complementary to all or part of a target nucleic acid in an insect
(
e.g., coleopteran) pest. In some embodiments an iRNA molecule may comprise polynucleotide(s)
that are complementary to all or part of a plurality of target nucleic acids; for
example, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more target nucleic acids. In particular embodiments,
an iRNA molecule may be produced
in vitro or
in vivo by a genetically-modified organism, such as a plant or bacterium. Also disclosed
are cDNAs that may be used for the production of dsRNA molecules, siRNA molecules,
miRNA molecules, shRNA molecules, and/or hpRNA molecules that are specifically complementary
to all or part of a target nucleic acid in an insect pest. Further described are recombinant
DNA constructs for use in achieving stable transformation of particular host targets.
Transformed host targets may express effective levels of dsRNA, siRNA, miRNA, shRNA,
and/or hpRNA molecules from the recombinant DNA constructs. Therefore, also described
is a plant transformation vector comprising at least one polynucleotide operably linked
to a heterologous promoter functional in a plant cell, wherein expression of the polynucleotide(s)
results in a RNA molecule comprising a string of contiguous nucleobases that is specifically
complementary to all or part of a target nucleic acid in an insect pest.
[0081] In particular examples, nucleic acid molecules useful for the control of insect
(e.g., coleopteran) pests may include: all or part of a native nucleic acid isolated from
Diabrotica comprising a
rpI1 polynucleotide
(e.g., any of SEQ ID NOs:1, 3, and 5-8); DNAs that when expressed result in a RNA molecule
comprising a polynucleotide that is specifically complementary to all or part of a
native RNA molecule that is encoded by
rpI1; iRNA molecules
(e.g., dsRNAs, siRNAs, miRNAs, shRNAs, and hpRNAs) that comprise at least one polynucleotide
that is specifically complementary to all or part of
rpI1; cDNAs that may be used for the production of dsRNA molecules, siRNA molecules, miRNA
molecules, shRNA molecules, and/or hpRNA molecules that are specifically complementary
to all or part of
rpI1; and recombinant DNA constructs for use in achieving stable transformation of particular
host targets, wherein a transformed host target comprises one or more of the foregoing
nucleic acid molecules.
B. Nucleic Acid Molecules
[0082] The present invention provides,
inter alia, iRNA
(e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) molecules that inhibit target gene expression
in a cell, tissue, or organ of an insect (
e.g., coleopteran) pest; and DNA molecules capable of being expressed as an iRNA molecule
in a cell or microorganism to inhibit target gene expression in a cell, tissue, or
organ of an insect pest.
[0083] Some embodiments of the invention provide an isolated nucleic acid molecule comprising
at least one
(e.g., one, two, three, or more) polynucleotide(s) selected from the group consisting of:
SEQ ID NOs:1 and 3; the complement of SEQ ID NO:1 or 3; a fragment of at least 15
contiguous nucleotides of SEQ ID NO:1 or 3
(e.g., any of SEQ ID NOs:5-8); the complement of a fragment of at least 15 contiguous nucleotides
of SEQ ID NO: 1 or 3; a native coding polynucleotide of a
Diabrotica organism
(e.g., WCR) comprising any of SEQ ID NOs:5-8; the complement of a native coding polynucleotide
of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; a fragment of at least 15 contiguous nucleotides
of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; and the complement of a fragment of at
least 15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8.
[0084] In particular embodiments, contact with or uptake by an insect (
e.g., coleopteran) pest of an iRNA transcribed from the isolated polynucleotide inhibits
the growth, development, and/or feeding of the pest.
[0085] In some embodiments, an isolated nucleic acid molecule of the invention may comprise
at least one
(e.g., one, two, three, or more) polynucleotide(s) selected from the group consisting of:
SEQ ID NO:75; the complement of SEQ ID NO:75; SEQ ID NO:76; the complement of SEQ
ID NO:76; SEQ ID NO:77; the complement of SEQ ID NO:77; SEQ ID NO:78; the complement
of SEQ ID NO:78; SEQ ID NO:79; the complement of SEQ ID NO:79; SEQ ID NO:80; the complement
of SEQ ID NO:80; a fragment of at least 15 contiguous nucleotides of any of SEQ ID
NOs:75-80, a fragment of at least 15 contiguous nucleotides of any of SEQ ID NOs:75,
a fragment of at least 15 contiguous nucleotides of any of SEQ ID NOs:76, a fragment
of at least 15 contiguous nucleotides of any of SEQ ID NOs:77, a fragment of at least
15 contiguous nucleotides of any of SEQ ID NOs:78, a fragment of at least 15 contiguous
nucleotides of any of SEQ ID NOs:79, or a fragment of at least 15 contiguous nucleotides
of any of SEQ ID NOs:80; the complement of a fragment of at least 15 contiguous nucleotides
of any of SEQ ID NOs:75-80, the complement of a fragment of at least 15 contiguous
nucleotides of any of SEQ ID NOs:75, the complement of a fragment of at least 15 contiguous
nucleotides of any of SEQ ID NOs:76, the complement of a fragment of at least 15 contiguous
nucleotides of any of SEQ ID NOs:77, the complement of a fragment of at least 15 contiguous
nucleotides of any of SEQ ID NOs:78, the complement of a fragment of at least 15 contiguous
nucleotides of any of SEQ ID NOs:79, or the complement of a fragment of at least 15
contiguous nucleotides of any of SEQ ID NOs:80; a native coding polynucleotide of
a
Diabrotica organism comprising any of SEQ ID NOs:77-80; the complement of a native coding polynucleotide
of a
Diabrotica organism comprising any of SEQ ID NOs:77-80; a fragment of at least 15 contiguous
nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:77-80, a fragment of at least 15 contiguous
nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:77, a fragment of at least 15 contiguous nucleotides
of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:78, a fragment of at least 15 contiguous nucleotides
of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:79, or a fragment of at least 15 contiguous
nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:80; and the complement of a fragment of at
least 15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:77-80, and the complement of a fragment of
at least 15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:77, and the complement of a fragment of at
least 15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:78, and the complement of a fragment of at
least 15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:79, or and the complement of a fragment of
at least 15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:80.
[0086] In particular embodiments, contact with or uptake by a coleopteran pest of the isolated
polynucleotide inhibits the growth, development, and/or feeding of the pest.
[0087] In certain embodiments, dsRNA molecules provided by the invention comprise polynucleotides
complementary to a transcript from a target gene comprising either of SEQ ID NOs:1
and 3, and fragments thereof, the inhibition of which target gene in an insect pest
results in the reduction or removal of a polypeptide or polynucleotide agent that
is essential for the pest's growth, development, or other biological function. A selected
polynucleotide may exhibit from about 80% to about 100% sequence identity to either
of SEQ ID NOs:1 and 3; a contiguous fragment of SEQ ID NOs:1 and 3; and the complement
of any of the foregoing. For example, a selected polynucleotide may exhibit about
79%; about 80%; about 81%; about 82%; about 83%; about 84%; about 85%; about 86%;
about 87%; about 88%; about 89%; about 90%; about 91%; about 92%; about 93%; about
94% about 95%; about 96%; about 97%; about 98%; about 98.5%; about 99%; about 99.5%;
or about 100% sequence identity to SEQ ID NOs:1 and/or about 79%; about 80%; about
81%; about 82%; about 83%; about 84%; about 85%; about 86%; about 87%; about 88%;
about 89%; about 90%; about 91%; about 92%; about 93%; about 94% about 95%; about
96%; about 97%; about 98%; about 98.5%; about 99%; about 99.5%; or about 100% sequence
identity to either of SEQ ID NOs:3; a contiguous fragment of either of SEQ ID NOs:1
and 3; and the complement of any of the foregoing.
[0088] In some embodiments, a DNA molecule capable of being expressed as an iRNA molecule
in a cell or microorganism to inhibit target gene expression may comprise a single
polynucleotide that is specifically complementary to all or part of a native polynucleotide
found in one or more target insect pest species (
e.
g., a coleopteran pest species), or the DNA molecule can be constructed as a chimera
from a plurality of such specifically complementary polynucleotides.
[0089] In some embodiments, a nucleic acid molecule may comprise a first and a second polynucleotide
separated by a "spacer." A spacer may be a region comprising any sequence of nucleotides
that facilitates secondary structure formation between the first and second polynucleotides,
where this is desired. In one embodiment, the spacer is part of a sense or antisense
coding polynucleotide for mRNA. The spacer may alternatively comprise any combination
of nucleotides or homologues thereof that are capable of being linked covalently to
a nucleic acid molecule.
[0090] For example, in some embodiments, the DNA molecule may comprise a polynucleotide
coding for one or more different iRNA molecules, wherein each of the different iRNA
molecules comprises a first polynucleotide and a second polynucleotide, wherein the
first and second polynucleotides are complementary to each other. The first and second
polynucleotides may be connected within a RNA molecule by a spacer. The spacer may
constitute part of the first polynucleotide or the second polynucleotide. Expression
of a RNA molecule comprising the first and second nucleotide polynucleotides may lead
to the formation of a dsRNA molecule, by specific intramolecular base-pairing of the
first and second nucleotide polynucleotides. The first polynucleotide or the second
polynucleotide may be substantially identical to a polynucleotide (
e.g., a target gene, or transcribed non-coding polynucleotide) native to an insect pest
(e.g., a coleopteran pest), a derivative thereof, or a complementary polynucleotide thereto.
[0091] dsRNA nucleic acid molecules comprise double strands of polymerized ribonucleotides,
and may include modifications to either the phosphate-sugar backbone or the nucleoside.
Modifications in RNA structure may be tailored to allow specific inhibition. In one
embodiment, dsRNA molecules may be modified through an ubiquitous enzymatic process
so that siRNA molecules may be generated. This enzymatic process may utilize an RNase
III enzyme, such as DICER in eukaryotes, either
in vitro or
in vivo. See Elbashir et al. (2001) Nature 411:494-8; and
Hamilton and Baulcombe (1999) Science 286(5441):950-2. DICER or functionally-equivalent RNase III enzymes cleave larger dsRNA strands and/or
hpRNA molecules into smaller oligonucleotides (
e.g., siRNAs), each of which is about 19-25 nucleotides in length. The siRNA molecules
produced by these enzymes have 2 to 3 nucleotide 3' overhangs, and 5' phosphate and
3' hydroxyl termini. The siRNA molecules generated by RNase III enzymes are unwound
and separated into single-stranded RNA in the cell. The siRNA molecules then specifically
hybridize with RNAs transcribed from a target gene, and both RNA molecules are subsequently
degraded by an inherent cellular RNA-degrading mechanism. This process may result
in the effective degradation or removal of the RNA encoded by the target gene in the
target organism. The outcome is the post-transcriptional silencing of the targeted
gene. In some embodiments, siRNA molecules produced by endogenous RNase III enzymes
from heterologous nucleic acid molecules may efficiently mediate the down-regulation
of target genes in insect pests.
[0092] In some embodiments, a nucleic acid molecule may include at least one non-naturally
occurring polynucleotide that can be transcribed into a single-stranded RNA molecule
capable of forming a dsRNA molecule
in vivo through intermolecular hybridization. Such dsRNAs typically self-assemble, and can
be provided in the nutrition source of an insect (
e.g., coleopteran) pest to achieve the post-transcriptional inhibition of a target gene.
In these and further embodiments, a nucleic acid molecule may comprise two different
non-naturally occurring polynucleotides, each of which is specifically complementary
to a different target gene in an insect pest. When such a nucleic acid molecule is
provided as a dsRNA molecule to, for example, a coleopteran pest, the dsRNA molecule
inhibits the expression of at least two different target genes in the pest.
C. Obtaining Nucleic Acid Molecules
[0093] A variety of polynucleotides in insect (
e.g., coleopteran) pests may be used as targets for the design of nucleic acid molecules,
such as iRNAs and DNA molecules encoding iRNAs. Selection of native polynucleotides
is not, however, a straight-forward process. For example, only a small number of native
polynucleotides in a coleopteran pest will be effective targets. It cannot be predicted
with certainty whether a particular native polynucleotide can be effectively down-regulated
by nucleic acid molecules of the invention, or whether down-regulation of a particular
native polynucleotide will have a detrimental effect on the growth, viability, and/or
development of an insect pest. The vast majority of native coleopteran pest polynucleotides,
such as ESTs isolated therefrom (for example, the coleopteran pest polynucleotides
listed in
U.S. Patent 7,612,194), do not have a detrimental effect on the growth and/or viability of the pest. Neither
is it predictable which of the native polynucleotides that may have a detrimental
effect on an insect pest are able to be used in recombinant techniques for expressing
nucleic acid molecules complementary to such native polynucleotides in a host plant
and providing the detrimental effect on the pest upon feeding without causing harm
to the host plant.
[0094] In some embodiments, nucleic acid molecules (
e.g., dsRNA molecules to be provided in the host plant of an insect (
e.g., coleopteran) pest) are selected to target cDNAs that encode proteins or parts of
proteins essential for pest growth and/or development, such as polypeptides involved
in metabolic or catabolic biochemical pathways, cell division, reproduction, energy
metabolism, digestion, host plant recognition, and the like. As described herein,
ingestion of compositions by a target pest organism containing one or more dsRNAs,
at least one segment of which is specifically complementary to at least a substantially
identical segment of RNA produced in the cells of the target pest organism, can result
in the death or other inhibition of the target. A polynucleotide, either DNA or RNA,
derived from an insect pest can be used to construct plant cells protected against
infestation by the pests. The host plant of the coleopteran pest
(e.g., Z. mays), for example, can be transformed to contain one or more polynucleotides derived from
the coleopteran pest as provided herein. The polynucleotide transformed into the host
may encode one or more RNAs that form into a dsRNA structure in the cells or biological
fluids within the transformed host, thus making the dsRNA available if/when the pest
forms a nutritional relationship with the transgenic host. This may result in the
suppression of expression of one or more genes in the cells of the pest, and ultimately
death or inhibition of its growth or development.
[0095] Thus, in some embodiments, a gene is targeted that is essentially involved in the
growth and development of an insect (
e.g., coleopteran) pest. Other target genes for use in the present invention may include,
for example, those that play important roles in pest viability, movement, migration,
growth, development, infectivity, and establishment of feeding sites. A target gene
may therefore be a housekeeping gene or a transcription factor. Additionally, a native
insect pest polynucleotide for use in the present invention may also be derived from
a homolog
(e.g., an ortholog), of a plant, viral, bacterial or insect gene, the function of which
is known to those of skill in the art, and the polynucleotide of which is specifically
hybridizable with a target gene in the genome of the target pest. Methods of identifying
a homolog of a gene with a known nucleotide sequence by hybridization are known to
those of skill in the art.
[0096] In some embodiments, the invention provides methods for obtaining a nucleic acid
molecule comprising a polynucleotide for producing an iRNA (
e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) molecule. One such embodiment comprises: (a)
analyzing one or more target gene(s) for their expression, function, and phenotype
upon dsRNA-mediated gene suppression in an insect (
e.g., coleopteran) pest; (b) probing a cDNA or gDNA library with a probe comprising all
or a portion of a polynucleotide or a homolog thereof from a targeted pest that displays
an altered
(e.g., reduced) growth or development phenotype in a dsRNA-mediated suppression analysis;
(c) identifying a DNA clone that specifically hybridizes with the probe; (d) isolating
the DNA clone identified in step (b); (e) sequencing the cDNA or gDNA fragment that
comprises the clone isolated in step (d), wherein the sequenced nucleic acid molecule
comprises all or a substantial portion of the RNA or a homolog thereof; and (f) chemically
synthesizing all or a substantial portion of a gene, or an siRNA, miRNA, hpRNA, mRNA,
shRNA, or dsRNA.
[0097] In further embodiments, a method for obtaining a nucleic acid fragment comprising
a polynucleotide for producing a substantial portion of an iRNA (
e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) molecule includes: (a) synthesizing first
and second oligonucleotide primers specifically complementary to a portion of a native
polynucleotide from a targeted insect (
e.g., coleopteran) pest; and (b) amplifying a cDNA or gDNA insert present in a cloning
vector using the first and second oligonucleotide primers of step (a), wherein the
amplified nucleic acid molecule comprises a substantial portion of a siRNA, miRNA,
hpRNA, mRNA, shRNA, or dsRNA molecule.
[0098] Nucleic acids can be isolated, amplified, or produced by a number of approaches.
For example, an iRNA (
e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) molecule may be obtained by PCR amplification
of a target polynucleotide (
e.g., a target gene or a target transcribed non-coding polynucleotide) derived from a gDNA
or cDNA library, or portions thereof. DNA or RNA may be extracted from a target organism,
and nucleic acid libraries may be prepared therefrom using methods known to those
ordinarily skilled in the art. gDNA or cDNA libraries generated from a target organism
may be used for PCR amplification and sequencing of target genes. A confirmed PCR
product may be used as a template for
in vitro transcription to generate sense and antisense RNA with minimal promoters. Alternatively,
nucleic acid molecules may be synthesized by any of a number of techniques
(See, e.g., Ozaki et al. (1992) Nucleic Acids Research, 20: 5205-5214; and
Agrawal et al. (1990) Nucleic Acids Research, 18: 5419-5423), including use of an automated DNA synthesizer (for example, a P.E. Biosystems,
Inc. (Foster City, Calif.) model 392 or 394 DNA/RNA Synthesizer), using standard chemistries,
such as phosphoramidite chemistry.
See, e.g., Beaucage et al. (1992) Tetrahedron, 48: 2223-2311;
U.S. Patents 4,980,460,
4,725,677,
4,415,732,
4,458,066, and
4,973,679. Alternative chemistries resulting in non-natural backbone groups, such as phosphorothioate,
phosphoramidate, and the like, can also be employed.
[0099] A RNA, dsRNA, siRNA, miRNA, shRNA, or hpRNA molecule of the present invention may
be produced chemically or enzymatically by one skilled in the art through manual or
automated reactions, or
in vivo in a cell comprising a nucleic acid molecule comprising a polynucleotide encoding
the RNA, dsRNA, siRNA, miRNA, shRNA, or hpRNA molecule. RNA may also be produced by
partial or total organic synthesis- any modified ribonucleotide can be introduced
by
in vitro enzymatic or organic synthesis. A RNA molecule may be synthesized by a cellular RNA
polymerase or a bacteriophage RNA polymerase
(e.g., T3 RNA polymerase, T7 RNA polymerase, and SP6 RNA polymerase). Expression constructs
useful for the cloning and expression of polynucleotides are known in the art.
See, e.g., International
PCT Publication No. WO97/32016; and
U.S. Patents 5,593,874,
5,698,425,
5,712,135,
5,789,214, and
5,804,693. RNA molecules that are synthesized chemically or by
in vitro enzymatic synthesis may be purified prior to introduction into a cell. For example,
RNA molecules can be purified from a mixture by extraction with a solvent or resin,
precipitation, electrophoresis, chromatography, or a combination thereof. Alternatively,
RNA molecules that are synthesized chemically or by
in vitro enzymatic synthesis may be used with no or a minimum of purification, for example,
to avoid losses due to sample processing. The RNA molecules may be dried for storage
or dissolved in an aqueous solution. The solution may contain buffers or salts to
promote annealing, and/or stabilization of dsRNA molecule duplex strands.
[0100] In embodiments, a dsRNA molecule may be formed by a single self-complementary RNA
strand or from two complementary RNA strands. dsRNA molecules may be synthesized either
in vivo or
in vitro. An endogenous RNA polymerase of the cell may mediate transcription of the one or
two RNA strands
in vivo, or cloned RNA polymerase may be used to mediate transcription
in vivo or
in vitro. Post-transcriptional inhibition of a target gene in an insect pest may be host-targeted
by specific transcription in an organ, tissue, or cell type of the host
(e.g., by using a tissue-specific promoter); stimulation of an environmental condition in
the host
(e.g., by using an inducible promoter that is responsive to infection, stress, temperature,
and/or chemical inducers); and/or engineering transcription at a developmental stage
or age of the host
(e.g., by using a developmental stage-specific promoter). RNA strands that form a dsRNA
molecule, whether transcribed
in vitro or
in vivo, may or may not be polyadenylated, and may or may not be capable of being translated
into a polypeptide by a cell's translational apparatus.
D. Recombinant Vectors and Host Cell Transformation
[0101] In some embodiments, the invention also provides a DNA molecule for introduction
into a cell
(e.g., a bacterial cell, a yeast cell, or a plant cell), wherein the DNA molecule comprises
a polynucleotide that, upon expression to RNA and ingestion by an insect
(e.g., coleopteran) pest, achieves suppression of a target gene in a cell, tissue, or organ
of the pest. Thus, some embodiments provide a recombinant nucleic acid molecule comprising
a polynucleotide capable of being expressed as an iRNA (
e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) molecule in a plant cell to inhibit target
gene expression in an insect pest. In order to initiate or enhance expression, such
recombinant nucleic acid molecules may comprise one or more regulatory elements, which
regulatory elements may be operably linked to the polynucleotide capable of being
expressed as an iRNA. Methods to express a gene suppression molecule in plants are
known, and may be used to express a polynucleotide of the present invention.
See, e.g., International
PCT Publication No. WO06/073727 and
U.S. Patent Publication No. 2006/0200878 A1)
[0102] In specific embodiments, a recombinant DNA molecule of the invention may comprise
a polynucleotide encoding a RNA that may form a dsRNA molecule. Such recombinant DNA
molecules may encode RNAs that may form dsRNA molecules capable of inhibiting the
expression of endogenous target gene(s) in an insect (
e.g., coleopteran) pest cell upon ingestion. In many embodiments, a transcribed RNA may
form a dsRNA molecule that may be provided in a stabilized form;
e.g., as a hairpin and stem and loop structure.
[0103] In some embodiments, one strand of a dsRNA molecule may be formed by transcription
from a polynucleotide which is substantially homologous to a polynucleotide selected
from the group consisting of SEQ ID NOs:1 and 3; the complements of SEQ ID NOs:1 and
3; a fragment of at least 15 contiguous nucleotides of either of SEQ ID NOs:1 and
3
(e.g., SEQ ID NOs:5-8); the complement of a fragment of at least 15 contiguous nucleotides
of either of SEQ ID NOs:1 and 3; a native coding polynucleotide of a
Diabrotica organism
(e.g., WCR) comprising any of SEQ ID NOs:5-8; the complement of a native coding polynucleotide
of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; a fragment of at least 15 contiguous nucleotides
of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; the complement of a fragment of at least
15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8.
[0104] In some embodiments, one strand of a dsRNA molecule may be formed by transcription
from a polynucleotide that is substantially homologous to a polynucleotide selected
from the group consisting of SEQ ID NOs:5-8; the complement of any of SEQ ID NOs:5-8;
fragments of at least 15 contiguous nucleotides of either of SEQ ID NOs:1 and 3; and
the complements of fragments of at least 15 contiguous nucleotides of either of SEQ
ID NOs:1 and 3.
[0105] In particular embodiments, a recombinant DNA molecule encoding a RNA that may form
a dsRNA molecule may comprise a coding region wherein at least two polynucleotides
are arranged such that one polynucleotide is in a sense orientation, and the other
polynucleotide is in an antisense orientation, relative to at least one promoter,
wherein the sense polynucleotide and the antisense polynucleotide are linked or connected
by a spacer of, for example, from about five (∼5) to about one thousand (∼1000) nucleotides.
The spacer may form a loop between the sense and antisense polynucleotides. The sense
polynucleotide or the antisense polynucleotide may be substantially homologous to
a target gene
(e.g., a
rpI1 gene comprising any of SEQ ID NOs:1, 3, and 5-8) or fragment thereof. In some embodiments,
however, a recombinant DNA molecule may encode a RNA that may form a dsRNA molecule
without a spacer. In embodiments, a sense coding polynucleotide and an antisense coding
polynucleotide may be different lengths.
[0106] Polynucleotides identified as having a deleterious effect on an insect pest or a
plant-protective effect with regard to the pest may be readily incorporated into expressed
dsRNA molecules through the creation of appropriate expression cassettes in a recombinant
nucleic acid molecule of the invention. For example, such polynucleotides may be expressed
as a hairpin with stem and loop structure by taking a first segment corresponding
to a target gene polynucleotide
(e.g., a
rpI1 gene comprising any of SEQ ID NOs:1, 3, and 5-8, and fragments of any of the foregoing);
linking this polynucleotide to a second segment spacer region that is not homologous
or complementary to the first segment; and linking this to a third segment, wherein
at least a portion of the third segment is substantially complementary to the first
segment. Such a construct forms a stem and loop structure by intramolecular base-pairing
of the first segment with the third segment, wherein the loop structure forms comprising
the second segment.
See, e.g., U.S. Patent Publication Nos. 2002/0048814 and
2003/0018993; and International
PCT Publication Nos. WO94/01550 and
WO98/05770. A dsRNA molecule may be generated, for example, in the form of a double-stranded
structure such as a stem-loop structure (
e.g., hairpin), whereby production of siRNA targeted for a native insect (
e.g., coleopteran) pest polynucleotide is enhanced by co-expression of a fragment of the
targeted gene, for instance on an additional plant expressible cassette, that leads
to enhanced siRNA production, or reduces methylation to prevent transcriptional gene
silencing of the dsRNA hairpin promoter.
[0107] Embodiments of the invention include introduction of a recombinant nucleic acid molecule
of the present invention into a plant
(i.e., transformation) to achieve insect
(e.g., coleopteran) pest-inhibitory levels of expression of one or more iRNA molecules.
A recombinant DNA molecule may, for example, be a vector, such as a linear or a closed
circular plasmid. The vector system may be a single vector or plasmid, or two or more
vectors or plasmids that together contain the total DNA to be introduced into the
genome of a host. In addition, a vector may be an expression vector. Nucleic acids
of the invention can, for example, be suitably inserted into a vector under the control
of a suitable promoter that functions in one or more hosts to drive expression of
a linked coding polynucleotide or other DNA element. Many vectors are available for
this purpose, and selection of the appropriate vector will depend mainly on the size
of the nucleic acid to be inserted into the vector and the particular host cell to
be transformed with the vector. Each vector contains various components depending
on its function (
e.g., amplification of DNA or expression of DNA) and the particular host cell with which
it is compatible.
[0108] To impart protection from an insect (
e.g., coleopteran) pest to a transgenic plant, a recombinant DNA may, for example, be transcribed
into an iRNA molecule
(e.g., a RNA molecule that forms a dsRNA molecule) within the tissues or fluids of the recombinant
plant. An iRNA molecule may comprise a polynucleotide that is substantially homologous
and specifically hybridizable to a corresponding transcribed polynucleotide within
an insect pest that may cause damage to the host plant species. The pest may contact
the iRNA molecule that is transcribed in cells of the transgenic host plant, for example,
by ingesting cells or fluids of the transgenic host plant that comprise the iRNA molecule.
Thus, in particular examples, expression of a target gene is suppressed by the iRNA
molecule within coleopteran pests that infest the transgenic host plant. In some embodiments,
suppression of expression of the target gene in a target coleopteran pest may result
in the plant being protected against attack by the pest.
[0109] In order to enable delivery of iRNA molecules to an insect pest in a nutritional
relationship with a plant cell that has been transformed with a recombinant nucleic
acid molecule of the invention, expression
(i.e., transcription) of iRNA molecules in the plant cell is required. Thus, a recombinant
nucleic acid molecule may comprise a polynucleotide of the invention operably linked
to one or more regulatory elements, such as a heterologous promoter element that functions
in a host cell, such as a bacterial cell wherein the nucleic acid molecule is to be
amplified, and a plant cell wherein the nucleic acid molecule is to be expressed.
[0110] Promoters suitable for use in nucleic acid molecules of the invention include those
that are inducible, viral, synthetic, or constitutive, all of which are well known
in the art. Non-limiting examples describing such promoters include
U.S. Patents 6,437,217 (maize RS81 promoter);
5,641,876 (rice actin promoter);
6,426,446 (maize RS324 promoter);
6,429,362 (maize PR-1 promoter);
6,232,526 (maize A3 promoter);
6,177,611 (constitutive maize promoters);
5,322,938,
5,352,605,
5,359,142, and
5,530,196 (CaMV 35S promoter);
6,433,252 (maize L3 oleosin promoter);
6,429,357 (rice actin 2 promoter, and rice actin 2 intron);
6,294,714 (light-inducible promoters);
6,140,078 (salt-inducible promoters);
6,252,138 (pathogen-inducible promoters);
6,175,060 (phosphorous deficiency-inducible promoters);
6,388,170 (bidirectional promoters);
6,635,806 (gamma-coixin promoter); and
U.S. Patent Publication No. 2009/757,089 (maize chloroplast aldolase promoter). Additional promoters include the nopaline
synthase (NOS) promoter (
Ebert et al. (1987) Proc. Natl. Acad. Sci. USA 84(16):5745-9) and the octopine synthase (OCS) promoters (which are carried on tumor-inducing plasmids
of
Agrobacterium tumefaciens); the caulimovirus promoters such as the cauliflower mosaic virus (CaMV) 19S promoter
(
Lawton et al. (1987) Plant Mol. Biol. 9:315-24); the CaMV 35S promoter (
Odell et al. (1985) Nature 313:810-2; the figwort mosaic virus 35S-promoter (
Walker et al. (1987) Proc. Natl. Acad. Sci. USA 84(19):6624-8); the sucrose synthase promoter (
Yang and Russell (1990) Proc. Natl. Acad. Sci. USA 87:4144-8); the R gene complex promoter (
Chandler et al. (1989) Plant Cell 1:1175-83); the chlorophyll a/b binding protein gene promoter; CaMV 35S (
U.S. Patents 5,322,938,
5,352,605,
5,359,142, and
5,530,196); FMV 35S (
U.S. Patents 6,051,753, and
5,378,619); a PC1SV promoter (
U.S. Patent 5,850,019); the SCP1 promoter (
U.S. Patent 6,677,503); and AGRtu.nos promoters (GenBank™ Accession No. V00087;
Depicker et al. (1982) J. Mol. Appl. Genet. 1:561-73;
Bevan et al. (1983) Nature 304:184-7).
[0111] In particular embodiments, nucleic acid molecules of the invention comprise a tissue-specific
promoter, such as a root-specific promoter. Root-specific promoters drive expression
of operably-linked coding polynucleotides exclusively or preferentially in root tissue.
Examples of root-specific promoters are known in the art.
See, e.g., U.S. Patents 5,110,732;
5,459,252 and
5,837,848; and
Opperman et al. (1994) Science 263:221-3; and
Hirel et al. (1992) Plant Mol. Biol. 20:207-18. In some embodiments, a polynucleotide or fragment for coleopteran pest control according
to the invention may be cloned between two root-specific promoters oriented in opposite
transcriptional directions relative to the polynucleotide or fragment, and which are
operable in a transgenic plant cell and expressed therein to produce RNA molecules
in the transgenic plant cell that subsequently may form dsRNA molecules, as described,
supra. The iRNA molecules expressed in plant tissues may be ingested by an insect pest
so that suppression of target gene expression is achieved.
[0112] Additional regulatory elements that may optionally be operably linked to a nucleic
acid include 5'UTRs located between a promoter element and a coding polynucleotide
that function as a translation leader element. The translation leader element is present
in fully-processed mRNA, and it may affect processing of the primary transcript, and/or
RNA stability. Examples of translation leader elements include maize and petunia heat
shock protein leaders (
U.S. Patent 5,362,865), plant virus coat protein leaders, plant rubisco leaders, and others.
See, e.g., Turner and Foster (1995) Molecular Biotech. 3(3):225-36. Non-limiting examples of 5'UTRs include GmHsp (
U.S. Patent 5,659,122); PhDnaK (
U.S. Patent 5,362,865); AtAnt1; TEV (
Carrington and Freed (1990) J. Virol. 64:1590-7); and AGRtunos (GenBank™ Accession No. V00087; and
Bevan et al. (1983) Nature 304:184-7).
[0113] Additional regulatory elements that may optionally be operably linked to a nucleic
acid also include 3' non-translated elements, 3' transcription termination regions,
or polyadenylation regions. These are genetic elements located downstream of a polynucleotide,
and include polynucleotides that provide polyadenylation signal, and/or other regulatory
signals capable of affecting transcription or mRNA processing. The polyadenylation
signal functions in plants to cause the addition of polyadenylate nucleotides to the
3' end of the mRNA precursor. The polyadenylation element can be derived from a variety
of plant genes, or from T-DNA genes. A non-limiting example of a 3' transcription
termination region is the nopaline synthase 3' region (nos 3';
Fraley et al. (1983) Proc. Natl. Acad. Sci. USA 80:4803-7). An example of the use of different 3' non-translated regions is provided in
Ingelbrecht et al., (1989) Plant Cell 1:671-80. Non-limiting examples of polyadenylation signals include one from a
Pisum sativum RbcS2 gene (Ps.RbcS2-E9;
Coruzzi et al. (1984) EMBO J. 3:1671-9) and AGRtu.nos (GenBank™ Accession No. E01312).
[0114] Some embodiments may include a plant transformation vector that comprises an isolated
and purified DNA molecule comprising at least one of the above-described regulatory
elements operatively linked to one or more polynucleotides of the present invention.
When expressed, the one or more polynucleotides result in one or more iRNA molecule(s)
comprising a polynucleotide that is specifically complementary to all or part of a
native RNA molecule in an insect (
e.g., coleopteran) pest. Thus, the polynucleotide(s) may comprise a segment encoding all
or part of a polyribonucleotide present within a targeted coleopteran pest RNA transcript,
and may comprise inverted repeats of all or a part of a targeted pest transcript.
A plant transformation vector may contain polynucleotides specifically complementary
to more than one target polynucleotide, thus allowing production of more than one
dsRNA for inhibiting expression of two or more genes in cells of one or more populations
or species of target insect pests. Segments of polynucleotides specifically complementary
to polynucleotides present in different genes can be combined into a single composite
nucleic acid molecule for expression in a transgenic plant. Such segments may be contiguous
or separated by a spacer.
[0115] In some embodiments, a plasmid of the present invention already containing at least
one polynucleotide(s) of the invention can be modified by the sequential insertion
of additional polynucleotide(s) in the same plasmid, wherein the additional polynucleotide(s)
are operably linked to the same regulatory elements as the original at least one polynucleotide(s).
In some embodiments, a nucleic acid molecule may be designed for the inhibition of
multiple target genes. In some embodiments, the multiple genes to be inhibited can
be obtained from the same insect
(e.g., coleopteran) pest species, which may enhance the effectiveness of the nucleic acid
molecule. In other embodiments, the genes can be derived from different insect pests,
which may broaden the range of pests against which the agent(s) is/are effective.
When multiple genes are targeted for suppression or a combination of expression and
suppression, a polycistronic DNA element can be engineered.
[0116] A recombinant nucleic acid molecule or vector of the present invention may comprise
a selectable marker that confers a selectable phenotype on a transformed cell, such
as a plant cell. Selectable markers may also be used to select for plants or plant
cells that comprise a recombinant nucleic acid molecule of the invention. The marker
may encode biocide resistance, antibiotic resistance
(e.g., kanamycin, Geneticin (G418), bleomycin, hygromycin,
etc.), or herbicide tolerance
(e.g., glyphosate,
etc.). Examples of selectable markers include, but are not limited to: a
neo gene which codes for kanamycin resistance and can be selected for using kanamycin,
G418,
etc.; a
bar gene which codes for bialaphos resistance; a mutant EPSP synthase gene which encodes
glyphosate tolerance; a
nitrilase gene which confers resistance to bromoxynil; a mutant acetolactate synthase (
ALS) gene which confers imidazolinone or sulfonylurea tolerance; and a methotrexate resistant
DHFR gene. Multiple selectable markers are available that confer resistance to ampicillin,
bleomycin, chloramphenicol, gentamycin, hygromycin, kanamycin, lincomycin, methotrexate,
phosphinothricin, puromycin, spectinomycin, rifampicin, streptomycin and tetracycline,
and the like. Examples of such selectable markers are illustrated in,
e.g., U.S. Patents 5,550,318;
5,633,435;
5,780,708 and
6,118,047.
[0118] In some embodiments, recombinant nucleic acid molecules, as described,
supra, may be used in methods for the creation of transgenic plants and expression of heterologous
nucleic acids in plants to prepare transgenic plants that exhibit reduced susceptibility
to insect
(e.g., coleopteran) pests. Plant transformation vectors can be prepared, for example, by
inserting nucleic acid molecules encoding iRNA molecules into plant transformation
vectors and introducing these into plants.
[0119] Suitable methods for transformation of host cells include any method by which DNA
can be introduced into a cell, such as by transformation of protoplasts
(See, e.g., U.S. Patent 5,508,184), by desiccation/inhibition-mediated DNA uptake
(See, e.g., Potrykus et al. (1985) Mol. Gen. Genet. 199:183-8), by electroporation (
See,
e.g., U.S. Patent 5,384,253), by agitation with silicon carbide fibers
(See, e.g., U.S. Patents 5,302,523 and
5,464,765), by
Agrobacterium-mediated transformation (
See,
e.
g.,
U.S. Patents 5,563,055;
5,591,616;
5,693,512;
5,824,877;
5,981,840; and
6,384,301), and by acceleration of DNA-coated particles (
See,
e.
g.,
U.S. Patents 5,015,580;
5,550,318;
5,538,880;
6,160,208;
6,399,861; and
6,403,865),
etc. Techniques that are particularly useful for transforming corn are described, for
example, in
U.S. Patents 7,060,876 and
5,591,616; and International
PCT Publication WO95/06722. Through the application of techniques such as these, the cells of virtually any
species may be stably transformed. In some embodiments, transforming DNA is integrated
into the genome of the host cell. In the case of multicellular species, transgenic
cells may be regenerated into a transgenic organism. Any of these techniques may be
used to produce a transgenic plant, for example, comprising one or more nucleic acids
encoding one or more iRNA molecules in the genome of the transgenic plant.
[0120] The most widely utilized method for introducing an expression vector into plants
is based on the natural transformation system of
Agrobacterium.
A. tumefaciens and A.
rhizogenes are plant pathogenic soil bacteria which genetically transform plant cells. The Ti
and Ri plasmids of A.
tumefaciens and A.
rhizogenes, respectively, carry genes responsible for genetic transformation of the plant. The
Ti (tumor-inducing)-plasmids contain a large segment, known as T-DNA, which is transferred
to transformed plants. Another segment of the Ti plasmid, the Vir region, is responsible
for T-DNA transfer. The T-DNA region is bordered by terminal repeats. In modified
binary vectors, the tumor-inducing genes have been deleted, and the functions of the
Vir region are utilized to transfer foreign DNA bordered by the T-DNA border elements.
The T-region may also contain a selectable marker for efficient recovery of transgenic
cells and plants, and a multiple cloning site for inserting polynucleotides for transfer
such as a dsRNA encoding nucleic acid.
[0121] Thus, in some embodiments, a plant transformation vector is derived from a Ti plasmid
of A.
tumefaciens (
See,
e.
g.,
U.S. Patents 4,536,475,
4,693,977,
4,886,937, and
5,501,967; and European Patent No.
EP 0 122 791) or a Ri plasmid of A.
rhizogenes. Additional plant transformation vectors include, for example and without limitation,
those described by
Herrera-Estrella et al. (1983) Nature 303:209-13;
Bevan et al. (1983) Nature 304:184-7;
Klee et al. (1985) Bio/Technol. 3:637-42; and in European Patent No.
EP 0 120 516, and those derived from any of the foregoing. Other bacteria such as
Sinorhizobium,
Rhizobium, and
Mesorhizobium that interact with plants naturally can be modified to mediate gene transfer to a
number of diverse plants. These plant-associated symbiotic bacteria can be made competent
for gene transfer by acquisition of both a disarmed Ti plasmid and a suitable binary
vector.
[0122] After providing exogenous DNA to recipient cells, transformed cells are generally
identified for further culturing and plant regeneration. In order to improve the ability
to identify transformed cells, one may desire to employ a selectable or screenable
marker gene, as previously set forth, with the transformation vector used to generate
the transformant. In the case where a selectable marker is used, transformed cells
are identified within the potentially transformed cell population by exposing the
cells to a selective agent or agents. In the case where a screenable marker is used,
cells may be screened for the desired marker gene trait.
[0123] Cells that survive the exposure to the selective agent, or cells that have been scored
positive in a screening assay, may be cultured in media that supports regeneration
of plants. In some embodiments, any suitable plant tissue culture media (
e.
g., MS and N6 media) may be modified by including further substances, such as growth
regulators. Tissue may be maintained on a basic medium with growth regulators until
sufficient tissue is available to begin plant regeneration efforts, or following repeated
rounds of manual selection, until the morphology of the tissue is suitable for regeneration
(
e.g., at least 2 weeks), then transferred to media conducive to shoot formation. Cultures
are transferred periodically until sufficient shoot formation has occurred. Once shoots
are formed, they are transferred to media conducive to root formation. Once sufficient
roots are formed, plants can be transferred to soil for further growth and maturation.
[0124] To confirm the presence of a nucleic acid molecule of interest (for example, a DNA
encoding one or more iRNA molecules that inhibit target gene expression in a coleopteran
pest) in the regenerating plants, a variety of assays may be performed. Such assays
include, for example: molecular biological assays, such as Southern and northern blotting,
PCR, and nucleic acid sequencing; biochemical assays, such as detecting the presence
of a protein product,
e.g., by immunological means (ELISA and/or western blots) or by enzymatic function; plant
part assays, such as leaf or root assays; and analysis of the phenotype of the whole
regenerated plant.
[0125] Integration events may be analyzed, for example, by PCR amplification using,
e.g., oligonucleotide primers specific for a nucleic acid molecule of interest. PCR genotyping
is understood to include, but not be limited to, polymerase-chain reaction (PCR) amplification
of gDNA derived from isolated host plant callus tissue predicted to contain a nucleic
acid molecule of interest integrated into the genome, followed by standard cloning
and sequence analysis of PCR amplification products. Methods of PCR genotyping have
been well described (for example,
Rios, G. et al. (2002) Plant J. 32:243-53) and may be applied to gDNA derived from any plant species
(e.g., Z. mays) or tissue type, including cell cultures.
[0126] A transgenic plant formed using
Agrobacterium-dependent transformation methods typically contains a single recombinant DNA inserted
into one chromosome. The polynucleotide of the single recombinant DNA is referred
to as a "transgenic event" or "integration event". Such transgenic plants are heterozygous
for the inserted exogenous polynucleotide. In some embodiments, a transgenic plant
homozygous with respect to a transgene may be obtained by sexually mating (selfing)
an independent segregant transgenic plant that contains a single exogenous gene to
itself, for example a T
0 plant, to produce T
1 seed. One fourth of the T
1 seed produced will be homozygous with respect to the transgene. Germinating T
1 seed results in plants that can be tested for heterozygosity, typically using an
SNP assay or a thermal amplification assay that allows for the distinction between
heterozygotes and homozygotes
(i.e., a zygosity assay).
[0127] In particular embodiments, at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 or more different
iRNA molecules are produced in a plant cell that have an insect (
e.g., coleopteran) pest-inhibitory effect. The iRNA molecules (
e.g., dsRNA molecules) may be expressed from multiple nucleic acids introduced in different
transformation events, or from a single nucleic acid introduced in a single transformation
event. In some embodiments, a plurality of iRNA molecules are expressed under the
control of a single promoter. In other embodiments, a plurality of iRNA molecules
are expressed under the control of multiple promoters. Single iRNA molecules may be
expressed that comprise multiple polynucleotides that are each homologous to different
loci within one or more insect pests (for example, the loci defined by SEQ ID NOs:1
and 3), both in different populations of the same species of insect pest, or in different
species of insect pests.
[0128] In addition to direct transformation of a plant with a recombinant nucleic acid molecule,
transgenic plants can be prepared by crossing a first plant having at least one transgenic
event with a second plant lacking such an event. For example, a recombinant nucleic
acid molecule comprising a polynucleotide that encodes an iRNA molecule may be introduced
into a first plant line that is amenable to transformation to produce a transgenic
plant, which transgenic plant may be crossed with a second plant line to introgress
the polynucleotide that encodes the iRNA molecule into the second plant line.
[0129] In some aspects, seeds and commodity products produced by transgenic plants derived
from transformed plant cells are included, wherein the seeds or commodity products
comprise a detectable amount of a nucleic acid of the invention. In some embodiments,
such commodity products may be produced, for example, by obtaining transgenic plants
and preparing food or feed from them. Commodity products comprising one or more of
the polynucleotides of the invention includes, for example and without limitation:
meals, oils, crushed or whole grains or seeds of a plant, and any food product comprising
any meal, oil, or crushed or whole grain of a recombinant plant or seed comprising
one or more of the nucleic acids of the invention. The detection of one or more of
the polynucleotides of the invention in one or more commodity or commodity products
is
de facto evidence that the commodity or commodity product is produced from a transgenic plant
designed to express one or more of the iRNA molecules of the invention for the purpose
of controlling insect (
e.
g., coleopteran) pests.
[0130] In some embodiments, a transgenic plant or seed comprising a nucleic acid molecule
of the invention also may comprise at least one other transgenic event in its genome,
including without limitation: a transgenic event from which is transcribed an iRNA
molecule targeting a locus in a coleopteran pest other than the one defined by SEQ
ID NO: 1 and SEQ ID NO: 3, such as, for example, one or more loci selected from the
group consisting of
Caf1-180 (
U.S. Patent Application Publication No. 2012/0174258);
VatpaseC (
U.S. Patent Application Publication No. 2012/0174259);
Rho1 (
U.S. Patent Application Publication No. 2012/0174260);
VatpaseH (
U.S. Patent Application Publication No. 2012/0198586);
PPI-87B (
U.S. Patent Application Publication No. 2013/0091600);
RPA70 (
U.S. Patent Application Publication No. 2013/0091601);
RPS6 (
U.S. Patent Application Publication No. 2013/0097730);
ROP (
U.S. Patent Application Publication No. 14/577811);
RNAPII (
U.S. Patent Application Publication No. 14/577854);
RNA polymerase II215 (
U.S. Patent Application No. 62/133202);
RNA polymerase 33 (
U.S. Patent Application No. 62/133210);
ncm (
U.S. Patent Application No. 62/095487);
Dre4 (
U.S. Patent Application No. 14/705,807);
COPI alpha (
U.S. Patent Application No. 62/063,199);
COPI beta (
U.S. Patent Application No. 62/063,203);
COPI gamma (
U.S. Patent Application No. 62/063,192); and
COPI delta (
U.S. Patent Application No. 62/063,216); a transgenic event from which is transcribed an iRNA molecule targeting a gene
in an organism other than a coleopteran pest
(e.g., a plant-parasitic nematode); a gene encoding an insecticidal protein
(e.g., a
Bacillus thuringiensis insecticidal protein); an herbicide tolerance gene
(e.g., a gene providing tolerance to glyphosate); and a gene contributing to a desirable
phenotype in the transgenic plant, such as increased yield, altered fatty acid metabolism,
or restoration of cytoplasmic male sterility. In particular embodiments, polynucleotides
encoding iRNA molecules of the invention may be combined with other insect control
and disease traits in a plant to achieve desired traits for enhanced control of plant
disease and insect damage. Combining insect control traits that employ distinct modes-of-action
may provide protected transgenic plants with superior durability over plants harboring
a single control trait, for example, because of the reduced probability that resistance
to the trait(s) will develop in the field.
V. Target Gene Suppression in an Insect Pest
A. Overview
[0131] In some embodiments of the invention, at least one nucleic acid molecule useful for
the control of insect (
e.g., coleopteran) pests may be provided to an insect pest, wherein the nucleic acid molecule
leads to RNAi-mediated gene silencing in the pest. In particular embodiments, an iRNA
molecule (
e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) may be provided to a coleopteran pest. In
some embodiments, a nucleic acid molecule useful for the control of insect pests may
be provided to a pest by contacting the nucleic acid molecule with the pest. In these
and further embodiments, a nucleic acid molecule useful for the control of insect
pests may be provided in a feeding substrate of the pest, for example, a nutritional
composition. In these and further embodiments, a nucleic acid molecule useful for
the control of an insect pest may be provided through ingestion of plant material
comprising the nucleic acid molecule that is ingested by the pest. In certain embodiments,
the nucleic acid molecule is present in plant material through expression of a recombinant
nucleic acid introduced into the plant material, for example, by transformation of
a plant cell with a vector comprising the recombinant nucleic acid and regeneration
of a plant material or whole plant from the transformed plant cell.
[0132] In some embodiments, a pest is contacted with the nucleic acid molecule that leads
to RNAi-mediated gene silencing in the pest through contact with a topical composition
(e.g., a composition applied by spraying) or an RNAi bait. RNAi baits are formed when the
dsRNA is mixed with food or an attractant or both. When the pests eat the bait, they
also consume the dsRNA. Baits may take the form of granules, gels, flowable powders,
liquids, or solids. In particular embodiments,
rpI1 may be incorporated into a bait formulation such as that described in
U.S. Patent No. 8,530,440 which is hereby incorporated by reference. Generally, with baits, the baits are placed
in or around the environment of the insect pest, for example, WCR can come into contact
with, and/or be attracted to, the bait.
B. RNAi-mediated Target Gene Suppression
[0133] In embodiments, the invention provides iRNA molecules (
e.g., dsRNA, siRNA, miRNA, shRNA, and hpRNA) that may be designed to target essential native
polynucleotides (
e.g., essential genes) in the transcriptome of an insect pest (for example, a coleopteran
(e.g., WCR, NCR, and SCR) pest), for example by designing an iRNA molecule that comprises
at least one strand comprising a polynucleotide that is specifically complementary
to the target polynucleotide. The sequence of an iRNA molecule so designed may be
identical to that of the target polynucleotide, or may incorporate mismatches that
do not prevent specific hybridization between the iRNA molecule and its target polynucleotide.
[0134] iRNA molecules of the invention may be used in methods for gene suppression in an
insect (
e.g., coleopteran) pest, thereby reducing the level or incidence of damage caused by the
pest on a plant (for example, a protected transformed plant comprising an iRNA molecule).
As used herein the term "gene suppression" refers to any of the well-known methods
for reducing the levels of protein produced as a result of gene transcription to mRNA
and subsequent translation of the mRNA, including the reduction of protein expression
from a gene or a coding polynucleotide including post-transcriptional inhibition of
expression and transcriptional suppression. Post-transcriptional inhibition is mediated
by specific homology between all or a part of an mRNA transcribed from a gene targeted
for suppression and the corresponding iRNA molecule used for suppression. Additionally,
post-transcriptional inhibition refers to the substantial and measurable reduction
of the amount of mRNA available in the cell for binding by ribosomes.
[0135] In embodiments wherein an iRNA molecule is a dsRNA molecule, the dsRNA molecule may
be cleaved by the enzyme, DICER, into short siRNA molecules (approximately 20 nucleotides
in length). The double-stranded siRNA molecule generated by DICER activity upon the
dsRNA molecule may be separated into two single-stranded siRNAs; the "passenger strand"
and the "guide strand." The passenger strand may be degraded, and the guide strand
may be incorporated into RISC. Post-transcriptional inhibition occurs by specific
hybridization of the guide strand with a specifically complementary polynucleotide
of an mRNA molecule, and subsequent cleavage by the enzyme, Argonaute (catalytic component
of the RISC complex).
[0136] In embodiments of the invention, any form of iRNA molecule may be used. Those of
skill in the art will understand that dsRNA molecules typically are more stable during
preparation and during the step of providing the iRNA molecule to a cell than are
single-stranded RNA molecules, and are typically also more stable in a cell. Thus,
while siRNA and miRNA molecules, for example, may be equally effective in some embodiments,
a dsRNA molecule may be chosen due to its stability.
[0137] In particular embodiments, a nucleic acid molecule is provided that comprises a polynucleotide,
which polynucleotide may be expressed
in vitro to produce an iRNA molecule that is substantially homologous to a nucleic acid molecule
encoded by a polynucleotide within the genome of an insect
(e.g., coleopteran) pest. In certain embodiments, the
in vitro transcribed iRNA molecule may be a stabilized dsRNA molecule that comprises a stem-loop
structure. After an insect pest contacts the
in vitro transcribed iRNA molecule, post-transcriptional inhibition of a target gene in the
pest (for example, an essential gene) may occur.
[0138] In some embodiments of the invention, expression of a nucleic acid molecule comprising
at least 15 contiguous nucleotides
(e.g., at least 19 contiguous nucleotides) of a polynucleotide are used in a method for
post-transcriptional inhibition of a target gene in an insect (
e.g., coleopteran) pest, wherein the polynucleotide is selected from the group consisting
of: SEQ ID NO:1; the complement of SEQ ID NO:1; SEQ ID NO:3; the complement of SEQ
ID NO:3; SEQ ID NO:5; the complement of SEQ ID NO:5; SEQ ID NO:6; the complement of
SEQ ID NO:6; SEQ ID NO:7; the complement of SEQ ID NO:7; SEQ ID NO:8; the complement
of SEQ ID NO:8; a fragment of at least 15 contiguous nucleotides of SEQ ID NO:1 and/or
SEQ ID NO:3; the complement of a fragment of at least 15 contiguous nucleotides of
SEQ ID NO:1 and/or SEQ ID NO:3; a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; the complement of a native coding polynucleotide
of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; a fragment of at least 15 contiguous nucleotides
of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8; the complement of a fragment of at least
15 contiguous nucleotides of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NOs:5-8. In certain embodiments, expression of
a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with any of the foregoing may be used. In certain embodiments, expression of a nucleic
acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with SEQ ID NO:1 may be used; in certain embodiments, expression of a nucleic acid
molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of SEQ ID NO:1 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with SEQ ID NO:3 may be used; in certain embodiments, expression of a nucleic acid
molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of SEQ ID NO:3 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with SEQ ID NO:5 may be used; in certain embodiments, expression of a nucleic acid
molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of SEQ ID NO:5 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with SEQ ID NO:6 may be used; in certain embodiments, expression of a nucleic acid
molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of SEQ ID NO:6 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with SEQ ID NO:7 may be used; in certain embodiments, expression of a nucleic acid
molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of SEQ ID NO:7 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with SEQ ID NO:8 may be used; in certain embodiments, expression of a nucleic acid
molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of SEQ ID NO:8 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of SEQ ID NO:1 may be used,
in certain embodiments, expression of a nucleic acid molecule that is at least about
80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of SEQ ID NO:3 may be used,
or in certain embodiments, expression of a nucleic acid molecule that is at least
about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of SEQ ID NO:1 and SEQ ID NO:3
may be used; in certain embodiments, expression of a nucleic acid molecule that is
at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of SEQ ID
NO:1 may be used, in certain embodiments, expression of a nucleic acid molecule that
is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of SEQ ID
NO:3 may be used; or in certain embodiments, expression of a nucleic acid molecule
that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of SEQ ID
NO:1 and SEQ ID NO:3 may be used; in certain embodiments, expression of a nucleic
acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a native coding polynucleotide of a
Diabrotica organism comprising SEQ ID NO:5 may be used, in certain embodiments, expression of
a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a native coding polynucleotide of a
Diabrotica organism comprising SEQ ID NO:6 may be used, in certain embodiments, expression of
a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a native coding polynucleotide of a
Diabrotica organism comprising SEQ ID NO:7 may be used, or in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a native coding polynucleotide of a
Diabrotica organism comprising SEQ ID NO:8 may be used; in certain embodiments, expression of
a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:5 may be used, in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:6 may be used, in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:7 may be used, or in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a native coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:8 may be used; in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of a native coding polynucleotide
of a
Diabrotica organism comprising SEQ ID NO:5 may be used, in certain embodiments, expression of
a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of a native coding polynucleotide
of a
Diabrotica organism comprising SEQ ID NO:6 may be used in certain embodiments, expression of
a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of a native coding polynucleotide
of a
Diabrotica organism comprising SEQ ID NO:7 may be used, or in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with a fragment of at least 15 contiguous nucleotides of a native coding polynucleotide
of a
Diabrotica organism comprising SEQ ID NO:8; in certain embodiments, expression of a nucleic
acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of a native
coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:5 may be used, in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of a native
coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:6 may be used, in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of a native
coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:7 may be used, or in certain embodiments, expression
of a nucleic acid molecule that is at least about 80% identical
(e.g., 79%, about 80%, about 81%, about 82%, about 83%, about 84%, about 85%, about 86%,
about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about
94%, about 95%, about 96%, about 97%, about 98%, about 99%, about 100%, and 100%)
with the complement of a fragment of at least 15 contiguous nucleotides of a native
coding polynucleotide of a
Diabrotica organism comprising any of SEQ ID NO:8 may be used. In these and further embodiments,
a nucleic acid molecule may be expressed that specifically hybridizes to a RNA molecule
present in at least one cell of an insect
(e.g., coleopteran) pest.
[0139] It is an important feature of some embodiments herein that the RNAi post-transcriptional
inhibition system is able to tolerate sequence variations among target genes that
might be expected due to genetic mutation, strain polymorphism, or evolutionary divergence.
The introduced nucleic acid molecule may not need to be absolutely homologous to either
a primary transcription product or a fully-processed mRNA of a target gene, so long
as the introduced nucleic acid molecule is specifically hybridizable to either a primary
transcription product or a fully-processed mRNA of the target gene. Moreover, the
introduced nucleic acid molecule may not need to be full-length, relative to either
a primary transcription product or a fully processed mRNA of the target gene.
[0140] Inhibition of a target gene using the iRNA technology of the present invention is
sequence-specific;
i.e., polynucleotides substantially homologous to the iRNA molecule(s) are targeted for
genetic inhibition. In some embodiments, a RNA molecule comprising a polynucleotide
with a nucleotide sequence that is identical to that of a portion of a target gene
may be used for inhibition. In these and further embodiments, a RNA molecule comprising
a polynucleotide with one or more insertion, deletion, and/or point mutations relative
to a target polynucleotide may be used. In particular embodiments, an iRNA molecule
and a portion of a target gene may share, for example, at least from about 80%, at
least from about 81%, at least from about 82%, at least from about 83%, at least from
about 84%, at least from about 85%, at least from about 86%, at least from about 87%,
at least from about 88%, at least from about 89%, at least from about 90%, at least
from about 91%, at least from about 92%, at least from about 93%, at least from about
94%, at least from about 95%, at least from about 96%, at least from about 97%, at
least from about 98%, at least from about 99%, at least from about 100%, and 100%
sequence identity. Alternatively, the duplex region of a dsRNA molecule may be specifically
hybridizable with a portion of a target gene transcript. In specifically hybridizable
molecules, a less than full length polynucleotide exhibiting a greater homology compensates
for a longer, less homologous polynucleotide. The length of the polynucleotide of
a duplex region of a dsRNA molecule that is identical to a portion of a target gene
transcript may be at least about 25, 50, 100, 200, 300, 400, 500, or at least about
1000 bases. In some embodiments, a polynucleotide of greater than 20-100 nucleotides
may be used. In particular embodiments, a polynucleotide of greater than about 100-500
nucleotides may be used. In particular embodiments, a polynucleotide of greater than
about 500-1000 nucleotides may be used, depending on the size of the target gene.
[0141] In certain embodiments, expression of a target gene in a pest (
e.g., coleopteran) may be inhibited by at least 10%; at least 33%; at least 50%; or at
least 80% within a cell of the pest, such that a significant inhibition takes place.
Significant inhibition refers to inhibition over a threshold that results in a detectable
phenotype (
e.g., cessation of growth, cessation of feeding, cessation of development, induced mortality,
etc.), or a detectable decrease in RNA and/or gene product corresponding to the target gene
being inhibited. Although, in certain embodiments of the invention, inhibition occurs
in substantially all cells of the pest, in other embodiments inhibition occurs only
in a subset of cells expressing the target gene.
[0142] In some embodiments, transcriptional suppression is mediated by the presence in a
cell of a dsRNA molecule exhibiting substantial sequence identity to a promoter DNA
or the complement thereof to effect what is referred to as "promoter trans suppression."
Gene suppression may be effective against target genes in an insect pest that may
ingest or contact such dsRNA molecules, for example, by ingesting or contacting plant
material containing the dsRNA molecules. dsRNA molecules for use in promoter trans
suppression may be specifically designed to inhibit or suppress the expression of
one or more homologous or complementary polynucleotides in the cells of the insect
pest. Post-transcriptional gene suppression by antisense or sense oriented RNA to
regulate gene expression in plant cells is disclosed in
U.S. Patents 5,107,065;
5,759,829;
5,283,184; and
5,231,020.
C. Expression of iRNA Molecules Provided to an Insect Pest
[0143] Expression of iRNA molecules for RNAi-mediated gene inhibition in an insect
(e.g., coleopteran) pest may be carried out in any one of many
in vitro or
in vivo formats. The iRNA molecules may then be provided to an insect pest, for example,
by contacting the iRNA molecules with the pest, or by causing the pest to ingest or
otherwise internalize the iRNA molecules. Some embodiments include transformed host
plants of a coleopteran pest, transformed plant cells, and progeny of transformed
plants. The transformed plant cells and transformed plants may be engineered to express
one or more of the iRNA molecules, for example, under the control of a heterologous
promoter, to provide a pest-protective effect. Thus, when a transgenic plant or plant
cell is consumed by an insect pest during feeding, the pest may ingest iRNA molecules
expressed in the transgenic plants or cells. The polynucleotides of the present invention
may also be introduced into a wide variety of prokaryotic and eukaryotic microorganism
hosts to produce iRNA molecules. The term "microorganism" includes prokaryotic and
eukaryotic species, such as bacteria and fungi.
[0144] Modulation of gene expression may include partial or complete suppression of such
expression. In another embodiment, a method for suppression of gene expression in
an insect (
e.g., coleopteran) pest comprises providing in the tissue of the host of the pest a gene-suppressive
amount of at least one dsRNA molecule formed following transcription of a polynucleotide
as described herein, at least one segment of which is complementary to an mRNA within
the cells of the insect pest. A dsRNA molecule, including its modified form such as
an siRNA, miRNA, shRNA, or hpRNA molecule, ingested by an insect pest may be at least
from about 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%,
95%, 96%, 97%, 98%, 99%, or about 100% identical to a RNA molecule transcribed from
a
rpI1 DNA molecule, for example, comprising a polynucleotide selected from the group consisting
of SEQ ID NOs:1, 3, and 5-8. Isolated and substantially purified nucleic acid molecules
including, but not limited to, non-naturally occurring polynucleotides and recombinant
DNA constructs for providing dsRNA molecules are therefore provided, which suppress
or inhibit the expression of an endogenous coding polynucleotide or a target coding
polynucleotide in an insect pest when introduced thereto.
[0145] Particular embodiments provide a delivery system for the delivery of iRNA molecules
for the post-transcriptional inhibition of one or more target gene(s) in an insect
(e.g., coleopteran) plant pest and control of a population of the plant pest. In some embodiments,
the delivery system comprises ingestion of a host transgenic plant cell or contents
of the host cell comprising RNA molecules transcribed in the host cell. In these and
further embodiments, a transgenic plant cell or a transgenic plant is created that
contains a recombinant DNA construct providing a stabilized dsRNA molecule of the
invention. Transgenic plant cells and transgenic plants comprising nucleic acids encoding
a particular iRNA molecule may be produced by employing recombinant DNA technologies
(which basic technologies are well-known in the art) to construct a plant transformation
vector comprising a polynucleotide encoding an iRNA molecule of the invention (
e.g., a stabilized dsRNA molecule); to transform a plant cell or plant; and to generate
the transgenic plant cell or the transgenic plant that contains the transcribed iRNA
molecule.
[0146] To impart insect (
e.g., coleopteran) pest protection to a transgenic plant, a recombinant DNA molecule may,
for example, be transcribed into an iRNA molecule, such as a dsRNA molecule, a siRNA
molecule, a miRNA molecule, a shRNA molecule, or a hpRNA molecule. In some embodiments,
a RNA molecule transcribed from a recombinant DNA molecule may form a dsRNA molecule
within the tissues or fluids of the recombinant plant. Such a dsRNA molecule may be
comprised in part of a polynucleotide that is identical to a corresponding polynucleotide
transcribed from a DNA within an insect pest of a type that may infest the host plant.
Expression of a target gene within the pest is suppressed by the dsRNA molecule, and
the suppression of expression of the target gene in the pest results in the transgenic
plant being protected against the pest. The modulatory effects of dsRNA molecules
have been shown to be applicable to a variety of genes expressed in pests, including,
for example, endogenous genes responsible for cellular metabolism or cellular transformation,
including house-keeping genes; transcription factors; molting-related genes; and other
genes which encode polypeptides involved in cellular metabolism or normal growth and
development.
[0147] For transcription from a transgene
in vivo or an expression construct, a regulatory region (
e.g., promoter, enhancer, silencer, and polyadenylation signal) may be used in some embodiments
to transcribe the RNA strand (or strands). Therefore, in some embodiments, as set
forth,
supra, a polynucleotide for use in producing iRNA molecules may be operably linked to one
or more promoter elements functional in a plant host cell. The promoter may be an
endogenous promoter, normally resident in the host genome. The polynucleotide of the
present invention, under the control of an operably linked promoter element, may further
be flanked by additional elements that advantageously affect its transcription and/or
the stability of a resulting transcript. Such elements may be located upstream of
the operably linked promoter, downstream of the 3' end of the expression construct,
and may occur both upstream of the promoter and downstream of the 3' end of the expression
construct.
[0148] Some embodiments provide methods for reducing the damage to a host plant
(e.g., a corn plant) caused by an insect (
e.g., coleopteran) pest that feeds on the plant, wherein the method comprises providing
in the host plant a transformed plant cell expressing at least one nucleic acid molecule
of the invention, wherein the nucleic acid molecule(s) functions upon being taken
up by the pest(s) to inhibit the expression of a target polynucleotide within the
pest(s), which inhibition of expression results in mortality and/or reduced growth
of the pest(s), thereby reducing the damage to the host plant caused by the pest(s).
In some embodiments, the nucleic acid molecule(s) comprise dsRNA molecules. In these
and further embodiments, the nucleic acid molecule(s) comprise dsRNA molecules that
each comprise more than one polynucleotide that is specifically hybridizable to a
nucleic acid molecule expressed in a coleopteran pest cell. In some embodiments, the
nucleic acid molecule(s) consist of one polynucleotide that is specifically hybridizable
to a nucleic acid molecule expressed in an insect pest cell.
[0149] In some embodiments, a method for increasing the yield of a corn crop is provided,
wherein the method comprises introducing into a corn plant at least one nucleic acid
molecule of the invention; cultivating the corn plant to allow the expression of an
iRNA molecule comprising the nucleic acid, wherein expression of an iRNA molecule
comprising the nucleic acid inhibits insect (
e.g., coleopteran) pest damage and/or growth, thereby reducing or eliminating a loss of
yield due to pest infestation. In some embodiments, the iRNA molecule is a dsRNA molecule.
In these and further embodiments, the nucleic acid molecule(s) comprise dsRNA molecules
that each comprise more than one polynucleotide that is specifically hybridizable
to a nucleic acid molecule expressed in an insect pest cell. In some examples, the
nucleic acid molecule(s) comprises a polynucleotide that is specifically hybridizable
to a nucleic acid molecule expressed in a coleopteran pest cell.
[0150] In some embodiments, a method for modulating the expression of a target gene in an
insect (
e.g., coleopteran) pest is provided, the method comprising: transforming a plant cell with
a vector comprising a polynucleotide encoding at least one iRNA molecule of the invention,
wherein the polynucleotide is operatively-linked to a promoter and a transcription
termination element; culturing the transformed plant cell under conditions sufficient
to allow for development of a plant cell culture including a plurality of transformed
plant cells; selecting for transformed plant cells that have integrated the polynucleotide
into their genomes; screening the transformed plant cells for expression of an iRNA
molecule encoded by the integrated polynucleotide; selecting a transgenic plant cell
that expresses the iRNA molecule; and feeding the selected transgenic plant cell to
the insect pest. Plants may also be regenerated from transformed plant cells that
express an iRNA molecule encoded by the integrated nucleic acid molecule. In some
embodiments, the iRNA molecule is a dsRNA molecule. In these and further embodiments,
the nucleic acid molecule(s) comprise dsRNA molecules that each comprise more than
one polynucleotide that is specifically hybridizable to a nucleic acid molecule expressed
in an insect pest cell. In some examples, the nucleic acid molecule(s) comprises a
polynucleotide that is specifically hybridizable to a nucleic acid molecule expressed
in a coleopteran pest cell.
[0151] iRNA molecules of the invention can be incorporated within the seeds of a plant species
(e.g., corn), either as a product of expression from a recombinant gene incorporated into
a genome of the plant cells, or as incorporated into a coating or seed treatment that
is applied to the seed before planting. A plant cell comprising a recombinant gene
is considered to be a transgenic event. Also included in embodiments of the invention
are delivery systems for the delivery of iRNA molecules to insect (
e.g., coleopteran) pests. For example, the iRNA molecules of the invention may be directly
introduced into the cells of a pest(s). Methods for introduction may include direct
mixing of iRNA with plant tissue from a host for the insect pest(s), as well as application
of compositions comprising iRNA molecules of the invention to host plant tissue. For
example, iRNA molecules may be sprayed onto a plant surface. Alternatively, an iRNA
molecule may be expressed by a microorganism, and the microorganism may be applied
onto the plant surface, or introduced into a root or stem by a physical means such
as an injection. As discussed,
supra, a transgenic plant may also be genetically engineered to express at least one iRNA
molecule in an amount sufficient to kill the insect pests known to infest the plant.
iRNA molecules produced by chemical or enzymatic synthesis may also be formulated
in a manner consistent with common agricultural practices, and used as spray-on products
for controlling plant damage by an insect pest. The formulations may include the appropriate
stickers and wetters required for efficient foliar coverage, as well as UV protectants
to protect iRNA molecules (
e.g., dsRNA molecules) from UV damage. Such additives are commonly used in the bioinsecticide
industry, and are well known to those skilled in the art. Such applications may be
combined with other spray-on insecticide applications (biologically based or otherwise)
to enhance plant protection from the pests.
[0152] All references, including publications, patents, and patent applications, cited herein
are hereby incorporated by reference to the extent they are not inconsistent with
the explicit details of this disclosure, and are so incorporated to the same extent
as if each reference were individually and specifically indicated to be incorporated
by reference and were set forth in its entirety herein. The references discussed herein
are provided solely for their disclosure prior to the filing date of the present application.
Nothing herein is to be construed as an admission that the inventors are not entitled
to antedate such disclosure by virtue of prior invention.
[0153] The following EXAMPLES are provided to illustrate certain particular features and/or
aspects. These EXAMPLES should not be construed to limit the disclosure to the particular
features or aspects described.
EXAMPLES
EXAMPLE 1: Materials and Methods
Sample preparation and bioassays
[0154] A number of dsRNA molecules (including those corresponding to
rpI1-
1 reg1 (SEQ ID NO:5),
rpI1-
2 reg2 (SEQ ID NO:6),
rpI1-
2 v1 (SEQ ID NO:7), and
rpI1-
2 v2 (SEQ ID NO:8) were synthesized and purified using a MEGASCRIPT
® RNAi kit or HiScribe
® T7 In Vitro Transcription Kit. The purified dsRNA molecules were prepared in TE buffer,
and all bioassays contained a control treatment consisting of this buffer, which served
as a background check for mortality or growth inhibition of WCR (
Diabrotica virgifera virgifera LeConte). The concentrations of dsRNA molecules in the bioassay buffer were measured
using a NANODROP™ 8000 spectrophotometer (THERMO SCIENTIFIC, Wilmington, DE).
[0155] Samples were tested for insect activity in bioassays conducted with neonate insect
larvae on artificial insect diet. WCR eggs were obtained from CROP CHARACTERISTICS,
INC. (Farmington, MN).
[0156] The bioassays were conducted in 128-well plastic trays specifically designed for
insect bioassays (C-D INTERNATIONAL, Pitman, NJ). Each well contained approximately
1.0 mL of an artificial diet designed for growth of coleopteran insects. A 60 µL aliquot
of dsRNA sample was delivered by pipette onto the surface of the diet of each well
(40 µL/cm
2). dsRNA sample concentrations were calculated as the amount of dsRNA per square centimeter
(ng/cm
2) of surface area (1.5 cm
2) in the well. The treated trays were held in a fume hood until the liquid on the
diet surface evaporated or was absorbed into the diet.
[0157] Within a few hours of eclosion, individual larvae were picked up with a moistened
camel hair brush and deposited on the treated diet (one or two larvae per well). The
infested wells of the 128-well plastic trays were then sealed with adhesive sheets
of clear plastic, and vented to allow gas exchange. Bioassay trays were held under
controlled environmental conditions (28 °C, ∼40% Relative Humidity, 16:8 (Light:Dark))
for 9 days, after which time the total number of insects exposed to each sample, the
number of dead insects, and the weight of surviving insects were recorded. Average
percent mortality and average growth inhibition were calculated for each treatment.
Growth inhibition (GI) was calculated as follows:
where TWIT is the Total Weight of live Insects in the Treatment;
TNIT is the Total Number of Insects in the Treatment;
TWIBC is the Total Weight of live Insects in the Background Check (Buffer control);
and
TNIBC is the Total Number of Insects in the Background Check (Buffer control).
[0158] The statistical analysis was done using JMP™ software (SAS, Cary, NC).
[0159] The LC
50 (Lethal Concentration) is defined as the dosage at which 50% of the test insects
are killed. The GI
50 (Growth Inhibition) is defined as the dosage at which the mean growth
(e.g. live weight) of the test insects is 50% of the mean value seen in Background Check
samples.
[0160] Replicated bioassays demonstrated that ingestion of particular samples resulted in
a surprising and unexpected mortality and growth inhibition of corn rootworm larvae.
EXAMPLE 2: Identification of Candidate Target Genes
[0161] Multiple stages of WCR (
Diabrotica virgifera virgifera LeConte) development were selected for pooled transcriptome analysis to provide candidate
target gene sequences for control by RNAi transgenic plant insect protection technology.
[0162] In one exemplification, total RNA was isolated from about 0.9 gm whole first-instar
WCR larvae; (4 to 5 days post-hatch; held at 16 °C), and purified using the following
phenol/TRI REAGENT
®-based method (MOLECULAR RESEARCH CENTER, Cincinnati, OH):
[0163] Larvae were homogenized at room temperature in a 15 mL homogenizer with 10 mL of
TRI REAGENT
® until a homogenous suspension was obtained. Following 5 min. incubation at room temperature,
the homogenate was dispensed into 1.5 mL microfuge tubes (1mL per tube), 200 µL of
chloroform was added, and the mixture was vigorously shaken for 15 seconds. After
allowing the extraction to sit at room temperature for 10 min, the phases were separated
by centrifugation at 12,000 x g at 4 °C. The upper phase (comprising about 0.6 mL)
was carefully transferred into another sterile 1.5 mL tube, and an equal volume of
room temperature isopropanol was added. After incubation at room temperature for 5
to 10 min, the mixture was centrifuged 8 min at 12,000 x g (4 °C or 25 °C).
[0164] The supernatant was carefully removed and discarded, and the RNA pellet was washed
twice by vortexing with 75% ethanol, with recovery by centrifugation for 5 min at
7,500 x g (4 °C or 25 °C) after each wash. The ethanol was carefully removed, the
pellet was allowed to air-dry for 3 to 5 min, and then was dissolved in nuclease-free
sterile water. RNA concentration was determined by measuring the absorbance (A) at
260 nm and 280 nm. A typical extraction from about 0.9 gm of larvae yielded over 1
mg of total RNA, with an A
260/A
280 ratio of 1.9. The RNA thus extracted was stored at -80 °C until further processed.
[0165] RNA quality was determined by running an aliquot through a 1% agarose gel. The agarose
gel solution was made using autoclaved 10x TAE buffer (Tris-acetate EDTA; 1x concentration
is 0.04 M Tris-acetate, 1 mM EDTA (ethylenediamine tetra-acetic acid sodium salt),
pH 8.0) diluted with DEPC (diethyl pyrocarbonate)-treated water in an autoclaved container.
1x TAE was used as the running buffer. Before use, the electrophoresis tank and the
well-forming comb were cleaned with RNaseAway™ (INVITROGEN INC., Carlsbad, CA). Two
µL of RNA sample were mixed with 8 µL of TE buffer (10 mM Tris HCl pH 7.0; 1 mM EDTA)
and 10 µL of RNA sample buffer (NOVAGEN
® Catalog No 70606; EMD4 Bioscience, Gibbstown, NJ). The sample was heated at 70 °C
for 3 min, cooled to room temperature, and 5 µL (containing 1 µg to 2 µg RNA) were
loaded per well. Commercially available RNA molecular weight markers were simultaneously
run in separate wells for molecular size comparison. The gel was run at 60 volts for
2 hrs.
[0166] A normalized cDNA library was prepared from the larval total RNA by a commercial
service provider (EUROFINS MWG Operon, Huntsville, AL), using random priming. The
normalized larval cDNA library was sequenced at 1/2 plate scale by GS FLX 454 Titanium™
series chemistry at EUROFINS MWG Operon, which resulted in over 600,000 reads with
an average read length of 348 bp. 350,000 reads were assembled into over 50,000 contigs.
Both the unassembled reads and the contigs were converted into BLASTable databases
using the publicly available program, FORMATDB (available from NCBI).
[0167] Total RNA and normalized cDNA libraries were similarly prepared from materials harvested
at other WCR developmental stages. A pooled transcriptome library for target gene
screening was constructed by combining cDNA library members representing the various
developmental stages.
[0168] Candidate genes for RNAi targeting were selected using information regarding lethal
RNAi effects of particular genes in other insects such as
Drosophila and
Tribolium. These genes were hypothesized to be essential for survival and growth in coleopteran
insects. Selected target gene homologs were identified in the transcriptome sequence
database as described below. Full-length or partial sequences of the target genes
were amplified by PCR to prepare templates for double-stranded RNA (dsRNA) production.
[0169] TBLASTN searches using candidate protein coding sequences were run against BLASTable
databases containing the unassembled
Diabrotica sequence reads or the assembled contigs. Significant hits to a
Diabrotica sequence (defined as better than e
-20 for contig homologies and better than e
-10 for unassembled sequence read homologies) were confirmed using BLASTX against the
NCBI non-redundant database. The results of this BLASTX search confirmed that the
Diabrotica homolog candidate gene sequences identified in the TBLASTN search indeed comprised
Diabrotica genes, or were the best hit to the non
-Diabrotica candidate gene sequence present in the
Diabrotica sequences. In a few cases, it was clear that some of the
Diabrotica contigs or unassembled sequence reads selected by homology to a non-
Diabrotica candidate gene overlapped, and that the assembly of the contigs had failed to join
these overlaps. In those cases, Sequencher™ v4.9 (GENE CODES CORPORATION, Ann Arbor,
MI) was used to assemble the sequences into longer contigs.
[0170] A candidate target gene encoding
Diabrotica rpI1 (SEQ ID NO:1 and SEQ ID NO:3) was identified as a gene that may lead to coleopteran
pest mortality, inhibition of growth, or inhibition of development in WCR. RNA polymerase
I-1 (
rpI1) encodes the largest subunit of RNA polymerase I (RNAPI).
Knackmuss et al. (1997) Mol. Gen. Genet. 253(5):529-34;
Seither et al. (1997) Mol. Gen. Genet. 255(2):180-6. In eukaryotes, the transcription of the genome is carried out by three distinct
classes of nuclear multi-subunit RNA polymerases (RNAP). RNAPI transcribes essential
genes which are involved in cellular processes, such as ribosome and protein biogenesis.
RNAPI activity is tightly co-regulated and dominates cellular transcription. The combined
expression exceeds 80% of total RNA synthesis and results in 1-2 million ribosomes
per cell generation.
[0171] RpI1 dsRNA transgenes can be combined with other dsRNA molecules to provide redundant
RNAi targeting and synergistic RNAi effects. Transgenic corn events expressing dsRNA
that targets
RpI1 are useful for preventing root feeding damage by corn rootworm.
RpI1 dsRNA transgenes represent new modes of action for combining with
Bacillus thuringiensis insecticidal protein technology in Insect Resistance Management gene pyramids to
mitigate against the development of rootworm populations resistant to either of these
rootworm control technologies.
[0172] Full-length or partial clones of sequences of a
Diabrotica candidate gene, herein referred to as
RpI1, were used to generate PCR amplicons for dsRNA synthesis.
EXAMPLE 3: Amplification of Target Genes to produce dsRNA
[0173] Primers were designed to amplify portions of coding regions of each target gene by
PCR.
Table 1. Where appropriate, a T7 phage promoter sequence (TTAATACGACTCACTATAGGGAGA; SEQ ID
NO:9) was incorporated into the 5' ends of the amplified sense or antisense strands.
Table 1. Total RNA was extracted from WCR using TRIzol
® (Life Technologies, Grand Island, NY), where WCR larvae and adults were homogenized
at room temperature in a 1.5 mL microfuge tube with 1 mL of TRIzol
® using a Pestle Motor Mixer (Cole-Parmer, Vernon Hills, IL) until a homogenous suspension
was obtained. Following 5 min. incubation at room temperature, the homogenate was
centrifuged to remove cell debris and 1 mL supernatant was transferred to a new tube.
200 µL of chloroform was added, and the mixture was vigorously shaken for 15 seconds.
After allowing the extraction to sit at room temperature for 2-3 min, the phases were
separated by centrifugation at 12,000 x g at 4 °C. The upper phase (comprising about
0.6 mL) was carefully transferred into another sterile 1.5 mL tube, and 500 uL of
room temperature isopropanol was added. After incubation at room temperature for 10
min, the mixture was centrifuged 10 min at 12,000 x g at 4 °C. The supernatant was
carefully removed and discarded, and the RNA pellet was washed twice by vortexing
with 75% ethanol, with recovery by centrifugation for 5 min at 7,500 x g (4 °C or
25 °C) after each wash. The ethanol was carefully removed, the pellet was allowed
to air-dry for 3 to 5 min, and then was dissolved in nuclease-free sterile water.
[0174] Total RNA was then used to make first-strand cDNA with SuperScriptIII
® First-Strand Synthesis System and manufacturers Oligo dT primed instructions (Life
Technologies, Grand Island, NY). This first-strand cDNA was used as template for PCR
reactions using opposing primers positioned to amplify all or part of the native target
gene sequence. dsRNA was also amplified from a DNA clone comprising the coding region
for a yellow fluorescent protein (YFP) (SEQ ID NO: 10;
Shagin et al. (2004) Mol. Biol. Evol. 21(5):841-50).
EXAMPLE 4: RNAi Constructs
Template preparation by PCR and dsRNA synthesis
[0175] A strategy used to provide specific templates for
rpI1 and YFP dsRNA production is shown in
FIG. 1. Template DNAs intended for use in
rpI1 dsRNA synthesis were prepared by PCR using the primer pairs in
Table 1 and (as PCR template) first-strand cDNA prepared from total RNA isolated from WCR
eggs, first-instar larvae, or adults. For each selected
rpI1 and YFP target gene region, PCR amplifications introduced a T7 promoter sequence
at the 5' ends of the amplified sense and antisense strands (the YFP segment was amplified
from a DNA clone of the YFP coding region). The two PCR amplified fragments for each
region of the target genes were then mixed in approximately equal amounts, and the
mixture was used as transcription template for dsRNA production.
See FIG. 1. The sequences of the dsRNA templates amplified with the particular primer pairs were:
SEQ ID NO:5 (
rpI1-1 reg1), SEQ ID NO:6 (
rpI1-2 reg2), SEQ ID NO:7 (
rpI1-2 v1), SEQ ID NO:8 (
rpl1-2 v2) and YFP (SEQ ID NO:10). Double-stranded RNA for insect bioassay was synthesized
and purified using an AMBION
® MEGASCRIPT
® RNAi kit following the manufacturer's instructions (INVITROGEN) or HiScube
® T7 In Vitro Transcription Kit following the manufacturer's instructions (New England
Biolabs, Ipswich, MA). The concentrations of dsRNAs were measured using a NANODROP™
8000 spectrophotometer (THERMO SCIENTIFIC, Wilmington, DE).
Construction of plant transformation vectors
[0176] Entry vectors harboring a target gene construct for hairpin formation comprising
segments of
rpI1 (SEQ ID NO:1 and SEQ ID NO:3) are assembled using a combination of chemically synthesized
fragments (DNA2.0, Menlo Park, CA) and standard molecular cloning methods. Intramolecular
hairpin formation by RNA primary transcripts is facilitated by arranging (within a
single transcription unit) two copies of a target gene segment in opposite orientation
to one another, the two segments being separated by a linker polynucleotide (
e.g., SEQ ID NO:83, and an ST-LS1 intron (
Vancanneyt et al. (1990) Mol. Gen. Genet. 220(2):245-50)). Thus, the primary mRNA transcript contains the two
rpI1 gene segment sequences as large inverted repeats of one another, separated by the
intron sequence. A copy of a promoter (
e.g. maize ubiquitin 1,
U.S. Patent No. 5,510,474; 35S from Cauliflower Mosaic Virus (CaMV); Sugarcane bacilliform badnavirus (ScBV)
promoter; promoters from rice actin genes; ubiquitin promoters; pEMU; MAS; maize H3
histone promoter; ALS promoter; phaseolin gene promoter;
cab; rubisco;
LAT52;
Zm13; and/or
apg) is used to drive production of the primary mRNA hairpin transcript, and a fragment
comprising a 3' untranslated region
(e.g., a maize peroxidase 5 gene (ZmPer5 3'UTR v2;
U.S. Patent No. 6,699,984), AtUbi10, AtEf1, or StPinII) is used to terminate transcription of the hairpin-RNA-expressing
gene.
[0177] Entry vector pDAB126156 comprises a
rpI1-2 v1-RNA construct (SEQ ID NO:81) that comprises a segment of
rpI1 (SEQ ID NO:7).
[0178] Entry vectors are used in standard GATEWAY
® recombination reactions with a typical binary destination vector to produce
rpI1 hairpin RNA expression transformation vectors for
Agrobacterium-mediated maize embryo transformations.
[0180] A negative control binary vector that comprises a gene that expresses a YFP protein
is constructed by means of standard GATEWAY
® recombination reactions with a typical binary destination vector and entry vector.
The binary destination vector comprises a herbicide tolerance gene (aryloxyalknoate
dioxygenase; AAD-1 v3) (as above) under the expression regulation of a maize ubiquitin
1 promoter (as above) and a fragment comprising a 3' untranslated region from a maize
lipase gene (ZmLip 3'UTR; as above). The entry vector comprises a YFP coding region
under the expression control of a maize ubiquitin 1 promoter (as above) and a fragment
comprising a 3' untranslated region from a maize peroxidase 5 gene (as above).
EXAMPLE 5: Screening of Candidate Target Genes
[0181] Synthetic dsRNA designed to inhibit target gene sequences identified in EXAMPLE 2
caused mortality and growth inhibition when administered to WCR in diet-based assays.
rpI1-2 reg2,
rpI1-2 v1 and
rpI1-2 v2 were observed to exhibit greatly increased efficacy in this assay over other dsRNAs
screened.
[0182] Replicated bioassays demonstrated that ingestion of dsRNA preparations derived from
rpI1-1 reg1,
rpI1-2 reg2,
rpI1-2 v1 and
rpI1-2 v2 each resulted in mortality and/or growth inhibition of western corn rootworm larvae.
Table 2 and
Table 3 show the results of diet-based feeding bioassays of WCR larvae following 9-day exposure
to these dsRNAs, as well as the results obtained with a negative control sample of
dsRNA prepared from a yellow fluorescent protein (YFP) coding region (SEQ ID NO: 10).
Table 2. Results of
rpI1 dsRNA diet feeding assays obtained with western corn rootworm larvae after 9 days
of feeding. ANOVA analysis found significance differences in Mean % Mortality and
Mean % Growth Inhibition (GI). Means were separated using the Tukey-Kramer test.
Gene Name |
Dose (ng/cm2) |
N |
Mean (%Mortality) ± SEM* |
Mean (GI) ± SEM |
rpI1-1 reg1 |
500 |
2 |
5.88±5.88 (B) |
0.55±0.00 (A) |
rpI1-2 reg2 |
500 |
10 |
77.67±8.10 (A) |
0.91±0.04 (A) |
rpI1-2 v1 |
500 |
10 |
79.41±6.97 (A) |
0.93±0.03 (A) |
rpI1-2 v2 |
500 |
10 |
65.55±4.97 (A) |
0.88±0.02 (A) |
TE** |
0 |
23 |
13.88±1.40 (B) |
0.08±0.04 (B) |
WATER |
0 |
23 |
13.59±2.06 (B) |
-0.10±0.06 (B) |
YFP*** |
500 |
23 |
14.62±2.00 (B) |
0.08±0.06 (B) |
*SEM =Standard Error of the Mean. Letters in parentheses designate statistical levels.
Levels not connected by same letter are significantly different (P<0.05).
**TE = Tris HCl (1 mM) plus EDTA (0.1 mM) buffer, pH7.2.
***YFP = Yellow Fluorescent Protein |
Table 3. Summary of oral potency of
rpI1 dsRNA on WCR larvae (ng/cm
2).
Gene Name |
LC50 |
Range |
GI50 |
Range |
rpI1-2 v1 |
25.9 |
36.78 - 53.29 |
17.41 |
6.21-48.77 |
rpI1-2 v2 |
176.65 |
255.29 - 399.79 |
58.52 |
32.69 - 104.73 |
[0183] It has previously been suggested that certain genes of
Diabrotica spp. may be exploited for RNAi-mediated insect control.
See U.S. Patent Publication No. 2007/0124836, which discloses 906 sequences, and
U.S. Patent No. 7,612,194, which discloses 9,112 sequences. However, it was determined that many genes suggested
to have utility for RNAi-mediated insect control are not efficacious in controlling
Diabrotica. It was also determined that sequences
rpI1-1 reg1,
rpI1-2 reg2,
rpI1-2 v1 and
rpI1-2 v2 each provide surprising and unexpected superior control of
Diabrotica, compared to other genes suggested to have utility for RNAi-mediated insect control.
[0184] For example,
annexin, beta spectrin 2, and
mtRP-L4 were each suggested in
U.S. Patent No. 7,612,194 to be efficacious in RNAi-mediated insect control. SEQ ID NO:19 is the DNA sequence
of
annexin region 1 (Reg 1) and SEQ ID NO:20 is the DNA sequence of
annexin region 2 (Reg 2). SEQ ID NO:21 is the DNA sequence of
beta spectrin 2 region 1 (Reg 1) and SEQ ID NO:22 is the DNA sequence of
beta spectrin 2 region 2 (Reg2). SEQ ID NO:23 is the DNA sequence of
mtRP-L4 region 1 (Reg 1) and SEQ ID NO:24 is the DNA sequence of
mtRP-L4 region 2 (Reg 2). A YFP sequence (SEQ ID NO:10) was also used to produce dsRNA as
a negative control.
[0185] Each of the aforementioned sequences was used to produce dsRNA by the methods of
EXAMPLE 3. The strategy used to provide specific templates for dsRNA production is
shown in
FIG. 2. Template DNAs intended for use in dsRNA synthesis were prepared by PCR using the
primer pairs in
Table 4 and (as PCR template) first-strand cDNA prepared from total RNA isolated from WCR
first-instar larvae. (YFP was amplified from a DNA clone.) For each selected target
gene region, two separate PCR amplifications were performed. The first PCR amplification
introduced a T7 promoter sequence at the 5' end of the amplified sense strands. The
second reaction incorporated the T7 promoter sequence at the 5' ends of the antisense
strands. The two PCR amplified fragments for each region of the target genes were
then mixed in approximately equal amounts, and the mixture was used as transcription
template for dsRNA production.
See FIG. 2. Double-stranded RNA was synthesized and purified using an AMBION
® MEGAscupt
® RNAi kit following the manufacturer's instructions (INVITROGEN). The concentrations
of dsRNAs were measured using a NANODROP™ 8000 spectrophotometer (THERMO SCIENTIFIC,
Wilmington, DE) and the dsRNAs were each tested by the same diet-based bioassay methods
described above.
Table 4 lists the sequences of the primers used to produce the
annexin Reg1,
annexin Reg2,
beta spectrin 2 Reg1,
beta spectrin 2 Reg2,
mtRP-L4 Reg1, and
mtRP-L4 Reg2 dsRNA molecules. YFP primer sequences for use in the method depicted in
FIG. 2 are also listed in
Table 4. Table 5 presents the results of diet-based feeding bioassays of WCR larvae following 9-day
exposure to these dsRNA molecules. Replicated bioassays demonstrated that ingestion
of these dsRNAs resulted in no mortality or growth inhibition of western corn rootworm
larvae above that seen with control samples of TE buffer, water, or YFP protein.
Table 5. Results of diet feeding assays obtained with western corn rootworm larvae after 9
days.
Gene Name |
Dose (ng/cm2) |
Mean Live Larval Weight (mg) |
Mean % Mortality |
Mean Growth Inhibition |
annexin-Reg 1 |
1000 |
0.545 |
0 |
-0.262 |
annexin-Reg 2 |
1000 |
0.565 |
0 |
-0.301 |
beta spectrin2 Reg 1 |
1000 |
0.340 |
12 |
-0.014 |
beta spectrin2 Reg 2 |
1000 |
0.465 |
18 |
-0.367 |
mtRP-L4 Reg 1 |
1000 |
0.305 |
4 |
-0.168 |
mtRP-L4 Reg 2 |
1000 |
0.305 |
7 |
-0.180 |
TE buffer* |
0 |
0.430 |
13 |
0.000 |
Water |
0 |
0.535 |
12 |
0.000 |
YFP** |
1000 |
0.480 |
9 |
-0.386 |
*TE = Tris HCl (10 mM) plus EDTA (1 mM) buffer, pH8.
**YFP = Yellow Fluorescent Protein |
EXAMPLE 6: Production of Transgenic Maize Tissues Comprising Insecticidal Hairpin
dsRNAs
[0186] Agrobacterium-mediated Transformation. Transgenic maize cells, tissues, and plants that produce one or more insecticidal
dsRNA molecules (for example, at least one dsRNA molecule including a dsRNA molecule
targeting a gene comprising
rpI1; SEQ ID NO:1 and SEQ ID NO:3) through expression of a chimeric gene stably-integrated
into the plant genome are produced following
Agrobacterium-mediated transformation. Maize transformation methods employing superbinary or binary transformation
vectors are known in the art, as described, for example, in
U.S. Patent 8,304,604, which is herein incorporated by reference in its entirety. Transformed tissues are
selected by their ability to grow on Haloxyfop-containing medium and are screened
for dsRNA production, as appropriate. Portions of such transformed tissue cultures
may be presented to neonate corn rootworm larvae for bioassay, essentially as described
in EXAMPLE 1.
[0187] Agrobacterium Culture Initiation. Glycerol stocks of
Agrobacterium strain DAt13192 cells (
WO 2012/016222A2) harboring a binary transformation vector described above (EXAMPLE 4) are streaked
on AB minimal medium plates (
Watson, et al. (1975) J. Bacteriol. 123:255-264) containing appropriate antibiotics, and are grown at 20 °C for 3 days. The cultures
are then streaked onto YEP plates (gm/L: yeast extract, 10; Peptone, 10; NaCl, 5)
containing the same antibiotics and are incubated at 20 °C for 1 day.
[0189] For each construct, 1 or 2 inoculating loops-full of
Agrobacterium from the YEP plate are suspended in 15 mL Inoculation Medium/acetosyringone stock
solution in a sterile, disposable, 50 mL centrifuge tube, and the optical density
of the solution at 550 nm (OD
550) is measured in a spectrophotometer. The suspension is then diluted to OD
550 of 0.3 to 0.4 using additional Inoculation Medium/acetosyringone. The tube of
Agrobacterium suspension is then placed horizontally on a platform shaker set at about 75 rpm at
room temperature and shaken for 1 to 4 hours while embryo dissection is performed.
[0190] Ear sterilization and embryo
isolation. Maize immature embryos are obtained from plants of
Zea mays inbred line B104 (
Hallauer et al. (1997) Crop Science 37:1405-1406), grown in the greenhouse and self- or sib-pollinated to produce ears. The ears are
harvested approximately 10 to 12 days post-pollination. On the experimental day, de-husked
ears are surface-sterilized by immersion in a 20% solution of commercial bleach (ULTRA
CLOROX® Germicidal Bleach, 6.15% sodium hypochlorite; with two drops of TWEEN 20)
and shaken for 20 to 30 min, followed by three rinses in sterile deionized water in
a laminar flow hood. Immature zygotic embryos (1.8 to 2.2 mm long) are aseptically
dissected from each ear and randomly distributed into microcentrifuge tubes containing
2.0 mL of a suspension of appropriate
Agrobacterium cells in liquid Inoculation Medium with 200 µM acetosyringone, into which 2 µL of
10% BREAK-THRU
® S233 surfactant (EVONIK INDUSTRIES; Essen, Germany) is added. For a given set of
experiments, embryos from pooled ears are used for each transformation.
[0191] Agrobacterium co-cultivation. Following isolation, the embryos are placed on a rocker platform for 5 minutes. The
contents of the tube are then poured onto a plate of Cocultivation Medium, which contains
4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L sucrose; 700 mg/L L-proline;
3.3 mg/L Dicamba in KOH (3,6-dichloro-o-anisic acid or 3,6-dichloro-2-methoxybenzoic
acid); 100 mg/L myo-inositol; 100 mg/L Casein Enzymatic Hydrolysate; 15 mg/L AgNO
3; 200 µM acetosyringone in DMSO; and 3 gm/L GELZAN™, at pH 5.8. The liquid
Agrobacterium suspension is removed with a sterile, disposable, transfer pipette. The embryos are
then oriented with the scutellum facing up using sterile forceps with the aid of a
microscope. The plate is closed, sealed with 3M™ MICROPORE™ medical tape, and placed
in an incubator at 25 °C with continuous light at approximately 60 µmol m
-2s
-1 of Photosynthetically Active Radiation (PAR).
[0192] Callus Selection and Regeneration of Transgenic Events. Following the CoCultivation period, embryos are transferred to Resting Medium, which
is composed of 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 30 gm/L sucrose; 700
mg/L L-proline; 3.3 mg/L Dicamba in KOH; 100 mg/L myo-inositol; 100 mg/L Casein Enzymatic
Hydrolysate; 15 mg/L AgNO
3; 0.5 gm/L MES (2-(N-morpholino)ethanesulfonic acid monohydrate; PHYTOTECHNOLOGIES
LABR.; Lenexa, KS); 250 mg/L Carbenicillin; and 2.3 gm/L GELZAN™; at pH 5.8. No more
than 36 embryos are moved to each plate. The plates are placed in a clear plastic
box and incubated at 27 °C with continuous light at approximately 50 µmol m
-2s
-1 PAR for 7 to 10 days. Callused embryos are then transferred (<18/plate) onto Selection
Medium I, which is comprised of Resting Medium (above) with 100 nM R-Haloxyfop acid
(0.0362 mg/L; for selection of calli harboring the
AAD-1 gene). The plates are returned to clear boxes and incubated at 27 °C with continuous
light at approximately 50 µmol m
-2s
-1 PAR for 7 days. Callused embryos are then transferred (<12/plate) to Selection Medium
II, which is comprised of Resting Medium (above) with 500 nM R-Haloxyfop acid (0.181
mg/L). The plates are returned to clear boxes and incubated at 27 °C with continuous
light at approximately 50 µmol m
-2s
-1 PAR for 14 days. This selection step allows transgenic callus to further proliferate
and differentiate.
[0193] Proliferating, embryogenic calli are transferred (<9/plate) to Pre-Regeneration medium.
Pre-Regeneration Medium contains 4.33 gm/L MS salts; 1X ISU Modified MS Vitamins;
45 gm/L sucrose; 350 mg/L L-proline; 100 mg/L myo-inositol; 50 mg/L Casein Enzymatic
Hydrolysate; 1.0 mg/L AgNO
3; 0.25 gm/L MES; 0.5 mg/L naphthaleneacetic acid in NaOH; 2.5 mg/L abscisic acid in
ethanol; 1 mg/L 6-benzylaminopurine; 250 mg/L Carbenicillin; 2.5 gm/L GELZAN™; and
0.181 mg/L Haloxyfop acid; at pH 5.8. The plates are stored in clear boxes and incubated
at 27 °C with continuous light at approximately 50 µmol m
-2s
-1 PAR for 7 days. Regenerating calli are then transferred (<6/plate) to Regeneration
Medium in PHYTATRAYS™ (SIGMA-ALDRICH) and incubated at 28 °C with 16 hours light/8
hours dark per day (at approximately 160 µmol m
-2s
-1 PAR) for 14 days or until shoots and roots develop. Regeneration Medium contains
4.33 gm/L MS salts; 1X ISU Modified MS Vitamins; 60 gm/L sucrose; 100 mg/L myo-inositol;
125 mg/L Carbenicillin; 3 gm/L GELLAN™ gum; and 0.181 mg/L R-Haloxyfop acid; at pH
5.8. Small shoots with primary roots are then isolated and transferred to Elongation
Medium without selection. Elongation Medium contains 4.33 gm/L MS salts; 1X ISU Modified
MS Vitamins; 30 gm/L sucrose; and 3.5 gm/L GELRITE™: at pH 5.8.
[0194] Transformed plant shoots selected by their ability to grow on medium containing Haloxyfop
are transplanted from PHYTATRAYS™ to small pots filled with growing medium (PROMIX
BX; PREMIER TECH HORTICULTURE), covered with cups or HUMI-DOMES (ARCO PLASTICS), and
then hardened-off in a CONVIRON growth chamber (27 °C day/24 °C night, 16-hour photoperiod,
50-70% RH, 200 µmol m
-2s
-1 PAR). In some instances, putative transgenic plantlets are analyzed for transgene
relative copy number by quantitative real-time PCR assays using primers designed to
detect the
AAD1 herbicide tolerance gene integrated into the maize genome. Further, RT-qPCR assays
are used to detect the presence of the linker sequence and/or of target sequence in
putative transformants. Selected transformed plantlets are then moved into a greenhouse
for further growth and testing.
[0195] Transfer and establishment of T0 plants in the greenhouse for bioassay and seed production. When plants reach the V3-V4 stage, they are transplanted into IE CUSTOM BLEND (PROFILE/METRO
MIX 160) soil mixture and grown to flowering in the greenhouse (Light Exposure Type:
Photo or Assimilation; High Light Limit: 1200 PAR; 16-hour day length; 27 °C day/24
°C night).
[0196] Plants to be used for insect bioassays are transplanted from small pots to TINUS™
350-4 ROOTRAINERS
® (SPENCER-LEMAIRE INDUSTRIES, Acheson, Alberta, Canada;) (one plant per event per
ROOTRAINER
®). Approximately four days after transplanting to ROOTRAINERS
®, plants are infested for bioassay.
[0197] Plants of the T
1 generation are obtained by pollinating the silks of T
0 transgenic plants with pollen collected from plants of non-transgenic inbred line
B104 or other appropriate pollen donors, and planting the resultant seeds. Reciprocal
crosses are performed when possible.
EXAMPLE 7: Molecular Analyses of Transgenic Maize Tissues
[0198] Molecular analyses (e.g. RT-qPCR) of maize tissues are performed on samples from
leaves that were collected from greenhouse grown plants on the day before or same
day that root feeding damage is assessed.
[0199] Results of RT-qPCR assays for the target gene are used to validate expression of
the transgene. Results of RT-qPCR assays for intervening sequence between repeat sequences
(which is integral to the formation of dsRNA hairpin molecules) in expressed RNAs
are alternatively used to validate the presence of hairpin transcripts. Transgene
RNA expression levels are measured relative to the RNA levels of an endogenous maize
gene.
[0200] DNA qPCR analyses to detect a portion of the
AAD1 coding region in gDNA are used to estimate transgene insertion copy number. Samples
for these analyses are collected from plants grown in environmental chambers. Results
are compared to DNA qPCR results of assays designed to detect a portion of a single-copy
native gene, and simple events (having one or two copies of the transgenes) are advanced
for further studies in the greenhouse.
[0201] Additionally, qPCR assays designed to detect a portion of the spectinomycin-resistance
gene (
SpecR; harbored on the binary vector plasmids outside of the T-DNA) are used to determine
if the transgenic plants contain extraneous integrated plasmid backbone sequences.
[0202] RNA transcript expression level: target qPCR. Callus cell events or transgenic plants are analyzed by real time quantitative PCR
(qPCR) of the target sequence to determine the relative expression level of the transgene,
as compared to the transcript level of an internal maize gene (for example, GENBANK
Accession No. BT069734), which encodes a TIP41-like protein
(i.e. a maize homolog of GENBANK Accession No. AT4G34270; having a tBLASTX score of 74%
identity). RNA is isolated using Norgen BioTek™ Total RNA Isolation Kit (Norgen, Thorold,
ON). The total RNA is subjected to an On-Column™ DNase1 treatment according to the
kit's suggested protocol. The RNA is then quantified on a NANODROP 8000 spectrophotometer
(THERMO SCIENTIFIC) and concentration is normalized to 50 ng/µL. First strand cDNA
is prepared using a HIGH CAPACITY cDNA SYNTHESIS KIT (INVITROGEN) in a 10 µL reaction
volume with 5 µL denatured RNA, substantially according to the manufacturer's recommended
protocol. The protocol is modified slightly to include the addition of 10 µL of 100
µM T20VN oligonucleotide (IDT) (TTTTTTTTTTTTTTTTTTTTVN, where V is A, C, or G, and
N is A, C, G, or T; SEQ ID NO:54) into the 1 mL tube of random primer stock mix, in
order to prepare a working stock of combined random primers and oligo dT.
[0203] Following cDNA synthesis, samples are diluted 1:3 with nuclease-free water, and stored
at -20 °C until assayed.
[0204] Separate real-time PCR assays for the target gene and TIP41-like transcript are performed
on a LIGHTCYCLER™ 480 (ROCHE DIAGNOSTICS, Indianapolis, IN) in 10 µL reaction volumes.
For the target gene assay, reactions are run with Primers rpI1 FWD Set 1 (SEQ ID NO:55)
and rpI1 REV Set 1 (SEQ ID NO:56), and an IDT Custom Oligo probe rpI1 PRB Set1, labeled
with FAM and double quenched with Zen and Iowa Black quenchers. For the TIP41-like
reference gene assay, primers TIPmxF (SEQ ID NO:57) and TIPmxR (SEQ ID NO:58), and
Probe HXTIP (SEQ ID NO:59) labeled with HEX (hexachlorofluorescein) are used.
[0205] All assays include negative controls of no-template (mix only). For the standard
curves, a blank (water in source well) is also included in the source plate to check
for sample cross-contamination. Primer and probe sequences are set forth in
Table 6. Reaction components recipes for detection of the various transcripts are disclosed
in
Table 7, and PCR reactions conditions are summarized in
Table 8. The FAM (6-Carboxy Fluorescein Amidite) fluorescent moiety is excited at 465 nm and
fluorescence is measured at 510 nm; the corresponding values for the HEX (hexachlorofluorescein)
fluorescent moiety are 533 nm and 580 nm.
Table 6. Oligonucleotide sequences used for molecular analyses of transcript levels in transgenic
maize.
Target |
Oligonucleotide |
Sequence |
rpI1 |
RPI-2v1 FWD Set 1 |
CCTCCACAAGATGAGTATGATGG (SEQ ID NO:55) |
rpI1 |
RPI-2v1 REV Set 1 |
GAGGTGCACGAGAGATTCATAC (SEQ ID NO:56) |
rlI1 |
RPI-2v1 PRB Set 1 |
/56-FAM/AAAGTCTTA/ZEN/CCCTGGTCGACGTTCC/3IABkFQ/ (SEQ ID NO:82) |
TIP41 |
TIPmxF |
TGAGGGTAATGCCAACTGGTT (SEQ NO:57) |
TIP41 |
TIPmxR |
GCAATGTAACCGAGTGTCTCTCAA (SEQ ID NO:58) |
TIP41 |
HXTIP (HEX-Probe) |
TTTTTGGCTTAGAGTTGATGGTGTACTGATGA (SEQ ID NO:59) |
Table 7. PCR reaction recipes for transcript detection.
|
rpI1 |
TIP-like Gene |
Component |
Final Concentration |
Roche Buffer |
1X |
1X |
rpI1 F |
0.4 µM |
0 |
rpI1 R |
0.4 µM |
0 |
rpI1 FAM |
0.2 µM |
0 |
HEXtipZM F |
0 |
0.4 µM |
HEXtipZM R |
0 |
0.4 µM |
HEXtipZMP (HEX) |
0 |
0.2 µM |
cDNA (2.0 µL) |
NA |
NA |
Water |
To 10 µL |
To 10 µL |
Table 8. Thermocycler conditions for RNA qPCR.
Target Gene and TIP41-like Gene Detection |
Process |
Temp. |
Time |
No. Cycles |
Target Activation |
95 °C |
10 min |
1 |
Denature |
95 °C |
10 sec |
40 |
Extend |
60 °C |
40 sec |
Acquire FAM or HEX |
72 °C |
1 sec |
Cool |
40 °C |
10 sec |
1 |
[0206] Data are analyzed using LIGHTCYCLER™ Software v1.5 by relative quantification using
a second derivative max algorithm for calculation of Cq values according to the supplier's
recommendations. For expression analyses, expression values are calculated using the
ΔΔCt method
(i.e., 2-(Cq TARGET - Cq REF)), which relies on the comparison of differences of Cq values
between two targets, with the base value of 2 being selected under the assumption
that, for optimized PCR reactions, the product doubles every cycle.
[0207] Transcript size and integrity: Northern Blot Assay. In some instances, additional molecular characterization of the transgenic plants
is obtained by the use of Northern Blot (RNA blot) analysis to determine the molecular
size of the
rpI1 linker RNA in transgenic plants expressing a
rpI1 linker dsRNA.
[0208] All materials and equipment are treated with RNaseZAP (AMBION/INVITROGEN) before
use. Tissue samples (100 mg to 500 mg) are collected in 2 mL SAFELOCK EPPENDORF tubes,
disrupted with a KLECKO™ tissue pulverizer (GARCIA MANUFACTURING, Visalia, CA) with
three tungsten beads in 1 mL of TRIZOL (INVITROGEN) for 5 min, then incubated at room
temperature (RT) for 10 min. Optionally, the samples are centrifuged for 10 min at
4 °C at 11,000 rpm and the supernatant is transferred into a fresh 2 mL SAFELOCK EPPENDORF
tube. After 200 µL chloroform are added to the homogenate, the tube is mixed by inversion
for 2 to 5 min, incubated at RT for 10 minutes, and centrifuged at 12,000 x g for
15 min at 4 °C. The top phase is transferred into a sterile 1.5 mL EPPENDORF tube,
600 µL of 100% isopropanol is added, followed by incubation at RT for 10 min to 2
hr, and then centrifuged at 12,000 x g for 10 min at 4 °C to 25 °C. The supernatant
is discarded and the RNA pellet is washed twice with 1 mL 70% ethanol, with centrifugation
at 7,500 x g for 10 min at 4 °C to 25 °C between washes. The ethanol is discarded
and the pellet is briefly air dried for 3 to 5 min before resuspending in 50 µL of
nuclease-free water.
[0209] Total RNA is quantified using the NANODROP 8000
® (THERMO-FISHER) and samples are normalized to 5 µg/10 µL. 10 µL of glyoxal (AMBION/INVITROGEN)
is then added to each sample. Five to 14 ng of DIG RNA standard marker mix (ROCHE
APPLIED SCIENCE, Indianapolis, IN) are dispensed and added to an equal volume of glyoxal.
Samples and marker RNAs are denatured at 50 °C for 45 min and stored on ice until
loading on a 1.25% SEAKEM GOLD agarose (LONZA, Allendale, NJ) gel in NORTHERNMAX 10
X glyoxal running buffer (AMBION/INVITROGEN). RNAs are separated by electrophoresis
at 65 volts/30 mA for 2 hours and 15 minutes.
[0210] Following electrophoresis, the gel is rinsed in 2X SSC for 5 min and imaged on a
GEL DOC station (BIORAD, Hercules, CA), then the RNA is passively transferred to a
nylon membrane (MILLIPORE) overnight at RT, using 10X SSC as the transfer buffer (20X
SSC consists of 3 M sodium chloride and 300 mM trisodium citrate, pH 7.0). Following
the transfer, the membrane is rinsed in 2X SSC for 5 minutes, the RNA is UV-crosslinked
to the membrane (AGILENT/STRATAGENE), and the membrane is allowed to dry at room temperature
for up to 2 days.
[0211] The membrane is pre-hybridized in ULTRAHYB™ buffer (AMBION/INVITROGEN) for 1 to 2
hr. The probe consists of a PCR amplified product containing the sequence of interest,
(for example, the antisense sequence portion of SEQ ID NOs:5- 8 or 81, as appropriate)
labeled with digoxigenin by means of a ROCHE APPLIED SCIENCE DIG procedure. Hybridization
in recommended buffer is overnight at a temperature of 60 °C in hybridization tubes.
Following hybridization, the blot is subjected to DIG washes, wrapped, exposed to
film for 1 to 30 minutes, then the film is developed, all by methods recommended by
the supplier of the DIG kit.
[0212] Transgene copy number determination. Maize leaf pieces approximately equivalent to 2 leaf punches are collected in 96-well
collection plates (QIAGEN). Tissue disruption is performed with a KLECKO™ tissue pulverizer
(GARCIA MANUFACTURING, Visalia, CA) in BIOSPRINT96 AP1 lysis buffer (supplied with
a BIOSPRINT96 PLANT KIT; QIAGEN) with one stainless steel bead. Following tissue maceration,
gDNA is isolated in high throughput format using a BIOSPRINT96 PLANT KIT and a BIOSPRINT96
extraction robot. gDNA is diluted 1:3 DNA:water prior to setting up the qPCR reaction.
[0213] qPCR analysis. Transgene detection by hydrolysis probe assay is performed by real-time PCR using
a LIGHTCYCLER
®480 system. Oligonucleotides to be used in hydrolysis probe assays to detect the target
gene
(e.g., rpI1), the linker sequence, and/or to detect a portion of the SpecR gene
(i.e., the spectinomycin resistance gene borne on the binary vector plasmids; SEQ ID NO:60;
SPC1 oligonucleotides in
Table 9), are designed using LIGHTCYCLER® PROBE DESIGN SOFTWARE 2.0. Further, oligonucleotides
to be used in hydrolysis probe assays to detect a segment of the AAD-1 herbicide tolerance
gene (SEQ ID NO:61; GAAD1 oligonucleotides in
Table 9) are designed using PRIMER EXPRESS software (APPLIED BIOSYSTEMS).
Table 9 shows the sequences of the primers and probes. Assays are multiplexed with reagents
for an endogenous maize chromosomal gene (Invertase (SEQ ID NO:62; GENBANK Accession
No: U16123; referred to herein as IVR1), which serves as an internal reference sequence
to ensure gDNA is present in each assay. For amplification, LIGHTCYCLER®480 PROBES
MASTER mix (ROCHE APPLIED SCIENCE) is prepared at 1x final concentration in a 10 µL
volume multiplex reaction containing 0.4 µM of each primer and 0.2 µM of each probe
(Table 10). A two step amplification reaction is performed as outlined in
Table 11. Fluorophore activation and emission for the FAM- and HEX-labeled probes are as described
above; CY5 conjugates are excited maximally at 650 nm and fluoresce maximally at 670
nm.
[0214] Cp scores (the point at which the fluorescence signal crosses the background threshold)
are determined from the real time PCR data using the fit points algorithm (LIGHTCYCLER
® SOFTWARE release 1.5) and the Relative Quant module (based on the ΔΔCt method). Data
are handled as described previously (above; RNA qPCR).
Table 9. Sequences of primers and probes (with fluorescent conjugate) used for gene copy number
determinations and binary vector plasmid backbone detection.
Name |
Sequence |
GAAD1-F |
TGTTCGGTTCCCTCTACCAA (SEQ ID NO:63) |
GAAD1-R |
CAACATCCATCACCTTGACTGA (SEQ NO:64) |
GAAD1-P (FAM) |
CACAGAACCGTCGCTTCAGCAACA (SEQ ID NO:65) |
IVR1-F |
TGGCGGACGACGACTTGT (SEQ NO:66) |
IVR1-R |
AAAGTTTGGAGGCTGCCGT (SEQ ID NO:67) |
IVR1-P (HEX) |
CGAGCAGACCGCCGTGTACTTCTACC (SEQ NO:68) |
SPC1A |
CTTAGCTGGATAACGCCAC (SEQ NO:69) |
SPC1S |
GACCGTAAGGCTTGATGAA (SEQ NO:70) |
TQSPEC (CY5*) |
CGAGATTCTCCGCGCTGTAGA (SEQ ID NO:71) |
LoopF |
GGAACGAGCTGCTTGCGTAT (SEQ ID NO:72) |
LoopR |
CACGGTGCAGCTGATTGATG (SEQ ID NO:73) |
Loop FAM |
TCCCTTCCGTAGTCAGAG (SEQ NO:74) |
Table 10. Reaction components for gene copy number analyses and plasmid backbone detection.
Component |
Amt. (µL) |
Stock |
Final Conc'n |
2x Buffer |
5.0 |
2x |
1x |
Appropriate Forward Primer |
0.4 |
10 µM |
0.4 |
Appropriate Reverse Primer |
0.4 |
10 µM |
0.4 |
Appropriate Probe |
0.4 |
5 µM |
0.2 |
IVR1-Forward Primer |
0.4 |
10 µM |
0.4 |
IVR1-Reverse Primer |
0.4 |
10 µM |
0.4 |
IVR1-Probe |
0.4 |
5 µM |
0.2 |
H2O |
0.6 |
NA* |
NA |
gDNA |
2.0 |
ND** |
ND |
Total |
10.0 |
|
|
*NA = Not Applicable
**ND = Not Determined |
Table 11. Thermocycler conditions for DNA qPCR.
Genomic copy number analyses |
Process |
Temp. |
Time |
No. Cycles |
Target Activation |
95 °C |
10 min |
1 |
Denature |
95 °C |
10 sec |
40 |
Extend & Acquire FAM, HEX, or CY5 |
60 °C |
40 sec |
Cool |
40 °C |
10 sec |
1 |
EXAMPLE 8: Bioassay of Transgenic Maize
[0215] Insect Bioassays. Bioactivity of dsRNA of the subject invention produced in plant cells is demonstrated
by bioassay methods.
See, e.g., Baum et al. (2007) Nat. Biotechnol. 25(11): 1322-1326. One is able to demonstrate efficacy, for example, by feeding various plant tissues
or tissue pieces derived from a plant producing an insecticidal dsRNA to target insects
in a controlled feeding environment. Alternatively, extracts are prepared from various
plant tissues derived from a plant producing the insecticidal dsRNA, and the extracted
nucleic acids are dispensed on top of artificial diets for bioassays as previously
described herein. The results of such feeding assays are compared to similarly conducted
bioassays that employ appropriate control tissues from host plants that do not produce
an insecticidal dsRNA, or to other control samples. Growth and survival of target
insects on the test diet is reduced compared to that of the control group.
[0216] Insect Bioassays with Transgenic Maize Events. Two western corn rootworm larvae (1 to 3 days old) hatched from washed eggs are selected
and placed into each well of the bioassay tray. The wells are then covered with a
"PULL N' PEEL " tab cover (BIO-CV-16, BIO-SERV) and placed in a 28 °C incubator with
an 18 hr:6 hr light:dark cycle. Nine days after the initial infestation, the larvae
are assessed for mortality, which is calculated as the percentage of dead insects
out of the total number of insects in each treatment. The insect samples are frozen
at -20 °C for two days, then the insect larvae from each treatment are pooled and
weighed. The percent of growth inhibition is calculated as the mean weight of the
experimental treatments divided by the mean of the average weight of two control well
treatments. The data are expressed as a Percent Growth Inhibition (of the negative
controls). Mean weights that exceed the control mean weight are normalized to zero.
[0217] Insect bioassays in the greenhouse. Western corn rootworm (WCR,
Diabrotica virgifera virgifera LeConte) eggs are received in soil from CROP CHARACTERISTICS (Farmington, MN). WCR
eggs are incubated at 28 °C for 10 to 11 days. Eggs are washed from the soil, placed
into a 0.15% agar solution, and the concentration is adjusted to approximately 75
to 100 eggs per 0.25 mL aliquot. A hatch plate is set up in a Petri dish with an aliquot
of egg suspension to monitor hatch rates.
[0218] The soil around the maize plants growing in ROOTRANERS
® is infested with 150 to 200 WCR eggs. The insects are allowed to feed for 2 weeks,
after which time a "Root Rating" is given to each plant. A Node-Injury Scale is utilized
for grading, essentially according to
Oleson et al. (2005) J. Econ. Entomol. 98:1-8. Plants passing this bioassay, showing reduced injury, are transplanted to 5-gallon
pots for seed production. Transplants are treated with insecticide to prevent further
rootworm damage and insect release in the greenhouses. Plants are hand pollinated
for seed production. Seeds produced by these plants are saved for evaluation at the
T
1 and subsequent generations of plants.
[0219] Transgenic negative control plants are generated by transformation with vectors harboring
genes designed to produce a yellow fluorescent protein (YFP). Non-transformed negative
control plants are grown from seeds of parental corn varieties from which the transgenic
plants were produced. Bioassays are conducted with negative controls included in each
set of plant materials.
EXAMPLE 9: Transgenic Zea mays Comprising Coleopteran Pest Sequences
[0220] 10-20 transgenic T
0 Zea mays plants are generated as described in EXAMPLE 6. A further 10-20 T
1 Zea mays independent lines expressing hairpin dsRNA for an RNAi construct are obtained for
corn rootworm challenge. Hairpin dsRNA comprise a portion of SEQ ID NO:1 and/or SEQ
ID NO:3 (
e.g., the hairpin dsRNA transcribed from SEQ ID NO:81). Additional hairpin dsRNAs are derived,
for example, from coleopteran pest sequences such as, for example, Caf1-180 (
U.S. Patent Application Publication No. 2012/0174258); VatpaseC (
U.S. Patent Application Publication No. 2012/0174259); Rho1 (
U.S. Patent Application Publication No. 2012/0174260); VatpaseH (
U.S. Patent Application Publication No. 2012/0198586); PPI-87B (
U.S. Patent Application Publication No. 2013/0091600); RPA70 (
U.S. Patent Application Publication No. 2013/0091601); RPS6 (
U.S. Patent Application Publication No. 2013/0097730);
RNA polymerase II215 (
U.S. Patent Application No. 62/133202);
RNA polymerase II33 (
U.S. Patent Application No.62/133210);
ROP (
U.S. Patent Application No. 14/577,811);
RNAPII140 (
U.S. Patent Application No. 14/577,854);
ncm (
U.S. Patent Application No. 62/095487);
Dre4 (
U.S. Patent Application No. 14/705,807);
COPI alpha (
U.S. Patent Application No. 62/063,199);
COPI beta (
U.S. Patent Application No. 62/063,203);
COPI gamma (
U.S. Patent Application No. 62/063,192); or
COPI delta (
U.S. Patent Application No. 62/063,216). These are confirmed through RT-PCR or other molecular analysis methods.
[0221] Total RNA preparations from selected independent T
1 lines are optionally used for RT-PCR with primers designed to bind in the linker
of the hairpin expression cassette in each of the RNAi constructs. In addition, specific
primers for each target gene in an RNAi construct are optionally used to amplify and
confirm the production of the pre-processed mRNA required for siRNA production
in planta. The amplification of the desired bands for each target gene confirms the expression
of the hairpin RNA in each transgenic
Zea mays plant. Processing of the dsRNA hairpin of the target genes into siRNA is subsequently
optionally confirmed in independent transgenic lines using RNA blot hybridizations.
[0222] Moreover, RNAi molecules having mismatch sequences with more than 80% sequence identity
to target genes affect corn rootworms in a way similar to that seen with RNAi molecules
having 100% sequence identity to the target genes. The pairing of mismatch sequence
with native sequences to form a hairpin dsRNA in the same RNAi construct delivers
plant-processed siRNAs capable of affecting the growth, development, and viability
of feeding coleopteran pests.
[0223] In planta delivery of dsRNA, siRNA, or miRNA corresponding to target genes and the subsequent
uptake by coleopteran pests through feeding results in down-regulation of the target
genes in the coleopteran pest through RNA-mediated gene silencing. When the function
of a target gene is important at one or more stages of development, the growth and/or
development of the coleopteran pest is affected, and in the case of at least one of
WCR, NCR, SCR, MCR, D.
balteata LeConte,
D. speciosa Germar, D.
u.
tenella, and D.
u.
undecimpunctata Mannerheim, leads to failure to successfully infest, feed, and/or develop, or leads
to death of the coleopteran pest. The choice of target genes and the successful application
of RNAi are then used to control coleopteran pests.
[0224] Phenotypic comparison of transgenic RNAi lines and nontransformed Zea mays. Target coleopteran pest genes or sequences selected for creating hairpin dsRNA have
no similarity to any known plant gene sequence. Hence, it is not expected that the
production or the activation of (systemic) RNAi by constructs targeting these coleopteran
pest genes or sequences will have any deleterious effect on transgenic plants. However,
development and morphological characteristics of transgenic lines are compared with
non-transformed plants, as well as those of transgenic lines transformed with an "empty"
vector having no hairpin-expressing gene. Plant root, shoot, foliage, and reproduction
characteristics are compared. Plant shoot characteristics such as height, leaf numbers
and sizes, time of flowering, floral size and appearance are recorded. In general,
there are no observable morphological differences between transgenic lines and those
without expression of target iRNA molecules when cultured
in vitro and in soil in the glasshouse.
EXAMPLE 10: Transgenic Zea mays Comprising a Coleopteran Pest Sequence and Additional RNAi Constructs
[0225] A transgenic
Zea mays plant comprising a heterologous coding sequence in its genome that is transcribed
into an iRNA molecule that targets an organism other than a coleopteran pest is secondarily
transformed
via Agrobacterium or WHISKERS™ methodologies
(see Petolino and Arnold (2009) Methods Mol. Biol. 526:59-67) to produce one or more insecticidal dsRNA molecules (for example, at least one dsRNA
molecule including a dsRNA molecule targeting a gene comprising SEQ ID NO:1 or SEQ
ID NO:3). Plant transformation plasmid vectors prepared essentially as described in
EXAMPLE 4 are delivered via
Agrobacterium or WHISKERS™-mediated transformation methods into maize suspension cells or immature
maize embryos obtained from a transgenic Hi II or B104
Zea mays plant comprising a heterologous coding sequence in its genome that is transcribed
into an iRNA molecule that targets an organism other than a coleopteran pest.
EXAMPLE 11: Transgenic Zea mays Comprising an RNAi Construct and Additional Coleopteran Pest Control Sequences